Polymer electrolyte, polymer electrolyte composition, battery, and electronic apparatus

ABSTRACT

A polymer electrolyte according to the invention is represented by the following formula (1). 
     
       
         
         
             
             
         
       
     
     In the formula (1), R 1  and R 2  are each independently hydrogen or CH 3 , R 3  is any of C 2 H 4 , CH(CH 3 )CH 2 , and (CH 2 ) 3 , m and n are each a copolymerization ratio of a structural unit in parentheses, and when m and n are set as follows: m+n=10, m and n satisfy the following formulae: 1≤m≤5 and 5≤n≤9, and p is 2 or more and 8 or less.

BACKGROUND 1. Technical Field

The present invention relates to a polymer electrolyte, a polymerelectrolyte composition, a battery, and an electronic apparatus.

2. Related Art

Heretofore, an all-solid-state battery using a solid electrolyte inplace of an organic electrolytic solution as an electrolyte has beenknown. For example, in JP-A-2008-117694 (Patent Document 1), a solidpolymer electrolyte composition (polymer electrolyte composition) whichis a specific copolymer has been proposed.

However, the solid polymer electrolyte composition disclosed in PatentDocument 1 has a problem that it is difficult to improve the ionconduction property as compared with an electrolyte using an organicelectrolytic solution. Therefore, when the solid polymer electrolytecomposition is used in a lithium battery or the like, it is difficult toensure a lithium ion conduction property, and there is a fear that asufficient battery capacity as a lithium battery cannot be ensured.

SUMMARY

An advantage of some aspects of the invention is to solve at least apart of the problems described above, and the invention and can beimplemented as the following forms or application examples.

Application Example

A polymer electrolyte according to this application example isrepresented by the following formula (1).

In the formula (1), R¹ and R² are each independently hydrogen or CH₃, R³is any of C₂H₄, CH(CH₃)CH₂, and (CH₂)₃, m and n are each acopolymerization ratio of a structural unit in parentheses, and when mand n are set as follows: m+n=10, m and n satisfy the followingformulae: 1≤m≤5 and 5≤n≤9, and p is 2 or more and 8 or less.

According to this application example, by using a((meth)acrylonitrile-polyalkylene glycol (meth)acrylate) copolymer whichis the polymer electrolyte of the formula (1) as a polymer electrolytecomposition (solid polymer electrolyte composition), the ion conductionproperty of the polymer electrolyte composition can be improved.Specifically, the polymer electrolyte composition has a cyano group(nitrile group) with a relatively large dielectric constant, andtherefore, the dielectric constant as the polymer electrolytecomposition can be increased. Due to this, the internal resistance ofthe polymer electrolyte composition is decreased, and thus, the ionconduction property is improved. Further, the polymer electrolytecomposition has a side chain having a polyalkylene glycol structure inaddition to a linear carbon main chain, and therefore, the molecularstructure is not bulky as compared with, for example, an aromatic ringstructure or an aliphatic ring structure, and the polymer electrolytecomposition is rich in flexibility. Therefore, an ion transfer pathwayis easily ensured, and the ion conduction property can be furtherimproved. Therefore, by using the polymer electrolyte composition in alithium battery or the like, the lithium ion conduction property isimproved, and the battery capacity can be increased.

In the polymer electrolyte according to the above-mentioned applicationexample, it is preferred that in the formula (1), when m and n are setas follows: m+n=10, m and n satisfy the following formulae: 2.5≤m≤5 and5≤n≤8.5.

According to this configuration, the content ratio of the cyano group isincreased, and therefore, in the polymer electrolyte composition, theinternal resistance is further decreased, and thus, the ion conductionproperty can be further improved.

Application Example

A polymer electrolyte composition according to this application examplecontains the polymer electrolyte according to the above-mentionedapplication example and a lithium salt compound.

According to this application example, an ion transfer pathway isensured by the polymer electrolyte, and the ionic activity coefficientof the lithium salt compound is increased. That is, an ion transferpathway corresponding to the increased ionic activity coefficient isensured, and therefore, ionic activation is promoted, and thus, thelithium ion conduction property can be improved. According to this, apolymer electrolyte composition suitable for a lithium battery can beprovided.

Application Example

A battery according to this application example includes an electrolytesection containing the polymer electrolyte composition according to theabove-mentioned application example, an assembly provided in contactwith the electrolyte section and containing an active material and anelectrolyte, and a current collector provided for the electrolytesection through the assembly.

According to this application example, by the above-mentioned polymerelectrolyte composition, a battery in which the ion conduction propertyof an electrolyte section is improved can be provided. That is, abattery capable of easily ensuring a desired battery capacity can beprovided.

In the battery according to the above-mentioned application example, itis preferred that the electrolyte contains the polymer electrolytecomposition according to the above-mentioned application example.

According to this configuration, the ion conduction property is improvednot only in the electrolyte section, but also in the assembly.Therefore, the ion conduction property in the battery can be furtherimproved. In addition, the polymer electrolyte has a linear carbon mainchain and a side chain having a polyalkylene glycol structure, andtherefore is relatively rich in flexibility. Due to this, by using thepolymer electrolyte in the assembly and the electrolyte section, thestrength against physical stress such as impact can be improved.

Application Example

A method for producing a polymer electrolyte composition according tothis application example includes preparing a solution containing aprecursor of a polymer electrolyte composition, which contains(meth)acrylonitrile, polyalkylene glycol (meth)acrylate, a lithium saltcompound, and a polymerization initiator, and forming the polymerelectrolyte composition by a polymerization reaction from the solutioncontaining the precursor.

According to this application example, a polymer electrolyte compositioncontaining a polymer electrolyte formed from (meth)acrylonitrile andpolyalkylene glycol (meth)acrylate is formed. That is, a polymerelectrolyte composition in which the lithium ion conduction property isimproved can be produced.

In the method for producing a polymer electrolyte composition accordingto the above-mentioned application example, it is preferred that thepreparing the solution containing the precursor includes preparing afirst solution by mixing polyalkylene glycol (meth)acrylate and alithium salt compound, preparing a second solution by mixing the firstsolution and a polymerization initiator, and preparing the solution bymixing the second solution and (meth)acrylonitrile.

According to this configuration, by mixing polyalkylene glycol(meth)acrylate and a lithium salt compound as a first solution, thesolubility of the lithium salt compound can be improved. Therefore, atime required for the step of preparing a solution containing aprecursor of a polymer electrolyte composition is reduced, and aproduction time for the polymer electrolyte composition can be reduced.Further, in the polymer electrolyte, uneven distribution of the lithiumsalt compound can be suppressed. Accordingly, the lithium ion conductionproperty is further improved.

In the method for producing a polymer electrolyte composition accordingto the above-mentioned application example, it is preferred that thepolymerization initiator contains at least one of a thermalpolymerization initiator and a photopolymerization initiator.

According to this configuration, by using at least one of polymerizationby heat and polymerization by an energy ray, the above-mentioned polymerelectrolyte can be formed.

Application Example

A method for producing a battery according to this application exampleincludes forming a molded body having a plurality of pores using anactive material, preparing a solution containing a precursor of apolymer electrolyte composition, which contains (meth)acrylonitrile,polyalkylene glycol (meth)acrylate, a lithium salt compound, and apolymerization initiator, bringing the solution containing the precursorinto contact with the molded body, forming an assembly containing thepolymer electrolyte composition and the molded body by polymerizing thesolution containing the precursor brought into contact with the moldedbody to form the polymer electrolyte composition, and forming a currentcollector so as to be in contact with the assembly.

According to this application example, a battery, which contains a((meth)acrylonitrile-polyalkylene glycol (meth)acrylate) copolymer as apolymer electrolyte composition and a lithium salt compound, and has animproved lithium ion conduction property can be produced. Further, thepolymer electrolyte composition and the molded body of the activematerial form an assembly, and therefore, a contact area between thepolymer electrolyte composition and the molded body is increased toreduce the interface impedance. Accordingly, a battery capable ofachieving favorable charge transfer at the interface between the polymerelectrolyte composition and the molded body can be produced.

Application Example

A method for producing a battery according to this application exampleincludes forming an assembly containing an active material and anelectrolyte, preparing a solution containing a precursor of a polymerelectrolyte composition, which contains (meth)acrylonitrile,polyalkylene glycol (meth)acrylate, a lithium salt compound, and apolymerization initiator, bringing the solution containing the precursorinto contact with the assembly, forming an electrolyte sectioncontaining the polymer electrolyte composition so as to be in contactwith the assembly by polymerizing the solution containing the precursor,and forming a current collector for the electrolyte section through theassembly.

According to this application example, the electrolyte section is formedcontaining a ((meth)acrylonitrile-polyalkylene glycol (meth)acrylate)copolymer and a lithium salt compound. Accordingly, a battery in whichthe lithium ion conduction property of the electrolyte section isimproved can be produced.

In the method for producing a battery according to the above-mentionedapplication example, it is preferred that the preparing the solutioncontaining the precursor includes preparing a first solution by mixingpolyalkylene glycol (meth)acrylate and a lithium salt compound,preparing a second solution by mixing the first solution and apolymerization initiator, and preparing the solution by mixing thesecond solution and (meth)acrylonitrile.

According to this configuration, in the step of preparing the solutioncontaining the precursor, the solubility of the lithium salt compound isimproved, and a production time for the battery can be reduced. Further,a battery in which uneven distribution of the lithium salt compound inthe polymer electrolyte composition is suppressed, and the lithium ionconduction property is further improved can be produced.

Application Example

A method for producing a battery according to this application exampleincludes preparing a mixture containing (meth)acrylonitrile,polyalkylene glycol (meth)acrylate, a lithium salt compound, apolymerization initiator, and an active material in the form ofparticles, forming a molded material in the form of a sheet using themixture, forming an assembly containing the active material and apolymer electrolyte composition obtained by polymerizing(meth)acrylonitrile and polyalkylene glycol (meth)acrylate using themolded material, and forming a current collector so as to be in contactwith the assembly.

According to this application example, a battery which contains a((meth)acrylonitrile-polyalkylene glycol (meth)acrylate) copolymer as apolymer electrolyte composition and a lithium salt compound, and has animproved lithium ion conduction property can be produced. Further, theassembly containing the polymer electrolyte composition and the activematerial is directly formed, and therefore, the production step of thebattery can be simplified.

In the method for producing a battery according to the above-mentionedapplication example, it is preferred that the preparing the mixtureincludes preparing a first solution by mixing polyalkylene glycol(meth)acrylate and a lithium salt compound, preparing a second solutionby mixing the first solution and a polymerization initiator, preparing asolution containing a precursor of a polymer electrolyte composition bymixing the second solution and (meth)acrylonitrile, and preparing themixture by mixing the solution containing the precursor and the activematerial in the form of particles.

According to this configuration, in the step of preparing the mixture,the solubility of the lithium salt compound is improved, and aproduction time for the battery can be reduced. Further, a battery inwhich uneven distribution of the lithium salt compound in the polymerelectrolyte composition is suppressed, and the lithium ion conductionproperty is further improved can be produced.

In the method for producing a battery according to the above-mentionedapplication example, it is preferred that the mixture contains aconduction aid.

According to this configuration, the electron conduction property can beimproved by the conduction aid.

Application Example

An electronic apparatus according to this application example includesthe battery according to the above-mentioned application example.

According to this application example, an electronic apparatus includinga battery having an improved lithium ion conduction property as a powersupply source can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic perspective view showing a configuration of alithium battery as a battery according to a first embodiment.

FIG. 2 is a schematic cross-sectional view showing a structure of thelithium battery.

FIG. 3 is a process flowchart showing a method for producing the lithiumbattery.

FIG. 4A is a schematic view showing the method for producing the lithiumbattery.

FIG. 4B is a schematic view showing the method for producing the lithiumbattery.

FIG. 4C is a schematic view showing the method for producing the lithiumbattery.

FIG. 4D is a schematic view showing the method for producing the lithiumbattery.

FIG. 4E is a schematic view showing the method for producing the lithiumbattery.

FIG. 4F is a schematic view showing the method for producing the lithiumbattery.

FIG. 4G is a schematic view showing the method for producing the lithiumbattery.

FIG. 5 is a table showing the compositions of polymer electrolytecompositions according to Examples and Comparative Examples.

FIG. 6 is a table showing the evaluation results of the lithium ionconduction property according to Examples and Comparative Examples.

FIG. 7 is a process flowchart showing a method for producing a lithiumbattery as a battery according to a second embodiment.

FIG. 8A is a schematic view showing the method for producing the lithiumbattery.

FIG. 8B is a schematic view showing the method for producing the lithiumbattery.

FIG. 8C is a schematic view showing the method for producing the lithiumbattery.

FIG. 8D is a schematic view showing the method for producing the lithiumbattery.

FIG. 9 is a schematic perspective view showing a configuration of alithium battery as a battery according to a third embodiment.

FIG. 10 is a process flowchart showing a method for producing thelithium battery.

FIG. 11 is a schematic view showing the method for producing the lithiumbattery.

FIG. 12 is a table showing the compositions of polymer electrolytecompositions according to Examples and Comparative Examples.

FIG. 13 is a table showing the compositions of polymer electrolytecompositions according to Examples and Comparative Examples.

FIG. 14 is a graph showing examples of Cole-Cole plots of the impedancespectra of Examples and Comparative Examples.

FIG. 15 is a table showing the evaluation results of the lithium ionconduction property according to Examples and Comparative Examples.

FIG. 16 is a schematic view showing a configuration of a wearableapparatus as an electronic apparatus according to a fourth embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described withreference to the drawings. Incidentally, in the following respectivedrawings, in order to make respective layers and respective members haverecognizable sizes, the scales of the respective layers and respectivemembers are made different from the actual ones.

First Embodiment

Battery

First, a battery according to this embodiment will be described withreference to FIG. 1. In this embodiment, a lithium battery will bedescribed as an example of the battery. FIG. 1 is a schematicperspective view showing a configuration of a lithium battery as thebattery according to the first embodiment.

As shown in FIG. 1, a lithium battery 100 of this embodiment includes anelectrolyte section 20 which contains a polymer electrolyte composition3, a positive electrode 9 as an assembly which is provided in contactwith the electrolyte section 20 and contains an active material 2 b andthe polymer electrolyte composition 3 as an electrolyte, and a firstcurrent collector 41 as a current collector which is provided for theelectrolyte section 20 through the positive electrode 9. The firstcurrent collector 41 is provided in contact with one surface 9 a of thepositive electrode 9. Further, the lithium battery 100 includes anegative electrode 30 which is provided for the positive electrode 9through the electrolyte section 20.

That is, the lithium battery 100 is a stacked body in which the firstcurrent collector 41, the positive electrode 9, the electrolyte section20, and the negative electrode 30 are sequentially stacked. A surfacewhich is in contact with the negative electrode 30 of the electrolytesection 20 is defined as “one surface 20 a”. Incidentally, for theelectrolyte section 20, a second current collector (not shown) may beprovided as appropriate through the negative electrode 30, and thelithium battery 100 may only have a current collector which is incontact with at least one of the positive electrode 9 and the negativeelectrode 30.

Current Collector

For the first current collector 41 and the second current collector, anymaterial can be suitably used as long as it is a forming material whichdoes not cause an electrochemical reaction with the positive electrode 9and the negative electrode 30, and has an electron conduction property.As the forming material of the first current collector 41 and the secondcurrent collector, for example, one type of metal (metal simplesubstance) selected from the group consisting of copper (Cu), magnesium(Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn),aluminum (Al), germanium (Ge), indium (In), gold (Au), platinum (Pt),silver (Ag), and palladium (Pd), or an alloy containing at least onetype of metal element selected from the above-mentioned group, aconductive metal oxide such as ITO (Tin-doped Indium Oxide), ATO(Antimony-doped Tin Oxide), or FTO (Fluorine-doped Tin Oxide), a metalnitride such as titanium nitride (TiN), zirconium nitride (ZrN), ortantalum nitride (TaN), or the like can be used.

As the form of the first current collector 41 and the second currentcollector, an appropriate form such as a metal foil, a plate, or a pasteobtained by kneading a conductive fine powder with a binder, other thana thin film of the forming material having an electron conductionproperty, can be selected according to the intended purpose. Theformation of the first current collector 41 and the second currentcollector may be performed after forming the positive electrode 9, thenegative electrode 30, and the like, or may be performed before formingsuch members.

Negative Electrode

As a negative electrode active material (forming material) contained inthe negative electrode 30, for example, niobium pentoxide (Nb₂O₅),vanadium pentoxide (V₂O₅), titanium oxide (TiO₂), indium oxide (In₂O₃),zinc oxide (ZnO), tin oxide (SnO₂), nickel oxide (NiO), tin (Sn)-dopedindium oxide (ITO), aluminum (Al)-doped zinc oxide (AZO), gallium(Ga)-doped zinc oxide (GZO), antimony (Sb)-doped tin oxide (ATO),fluorine (F)-doped tin oxide (FTO), anatase-phase TiO₂, a lithiumcomposite oxide such as Li₄Ti₅O₁₂ or Li₂Ti₃O₇, a metal or an alloy suchas lithium (Li), silicon (Si), tin (Sn), a silicon-manganese alloy(Si—Mn), a silicon-cobalt alloy (Si—Co), a silicon-nickel alloy (Si—Ni),indium (In), or gold (Au), a carbon material, a material obtained byintercalation of lithium ions between layers of a carbon material, orthe like can be used.

The thickness of the negative electrode 30 is preferably about 50 nm to100 μm or so, but can be arbitrarily designed according to a desiredbattery capacity or material properties.

The lithium battery 100 has, for example, a circular disk shape, and thesize of the outer shape thereof is such that the diameter is about 10 mmand the thickness is about 150 μm. In addition to being small and thin,the lithium battery 100 can be charged and discharged, and is capable ofobtaining a large output energy, and therefore can be favorably used asa power supply source (power supply) for a portable information terminalor the like. The shape of the lithium battery 100 is not limited to acircular disk shape, and may be, for example, a polygonal disk shape.Such a thin lithium battery 100 may be used alone or a plurality oflithium batteries 100 may be stacked and used. In the case of stackingthe lithium batteries 100, in the lithium batteries 100, the firstcurrent collector 41 and the second current collector are notnecessarily essential components, and a configuration in which one ofthe current collectors is included may be adopted.

Next, the structures of the positive electrode 9, the electrolytesection 20, and the like included in the lithium battery 100 will bedescribed with reference to FIG. 2. FIG. 2 is a schematiccross-sectional view showing the structure of the lithium battery.

As described above, the electrolyte section 20 contains the polymerelectrolyte composition 3, and the positive electrode 9 contains theactive material 2 b and the polymer electrolyte composition 3. Theactive material 2 b is in the form of particles, and a plurality ofparticles of the active material 2 b gather to form an active materialsection 2 having a plurality of pores.

Positive Electrode

The active material section 2 included in the positive electrode 9 is anaggregate of the active material 2 b in the form of particles and has aplurality of pores. The plurality of pores communicate with one anotherin a mesh-like manner inside the active material section 2. Therefore,the contact between the particles of the active material 2 b is ensured.The polymer electrolyte composition 3 is provided so as to fill theplurality of pores of the active material section 2 and further coverthe entire active material section 2. That is, the active materialsection 2 and the polymer electrolyte composition 3 are assembled toform an assembly (positive electrode 9). Therefore, as compared with thecase where the active material section 2 does not have a plurality ofpores or the case where the polymer electrolyte composition 3 is notprovided in the pores, the contact area between the active material 2 band the polymer electrolyte composition 3 becomes large. Due to this,the interface resistance is reduced, and it becomes possible to achievefavorable charge transfer at the interface between the active materialsection 2 and the polymer electrolyte composition 3.

As in the lithium battery 100 according to the embodiment, in the casewhere the first current collector 41 is used on the positive electrodeside, as the forming material (positive electrode active material) ofthe active material 2 b, a generally known lithium composite metalcompound can be used. FIG. 2 is a view schematically showing the activematerial 2 b, and the particle diameter or size thereof is notnecessarily the same as the actual one.

The lithium composite metal compound to be used in the positiveelectrode active material refers to a compound such as an oxide, whichcontains lithium and also contains two or more types of metal elementsas a whole, and in which the existence of oxoacid ion is not observed.

Examples of the lithium composite metal compound include composite metalcompounds containing lithium (Li) and also containing at least one typeof element selected from vanadium (V), chromium (Cr), manganese (Mn),iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). Such a compositemetal compound is not particularly limited, however, specific examplesthereof include LiCoO₂, LiNiO₂, LiMn₂O₄, Li₂Mn₂O₃, LiCr_(0.5)Mn_(0.5)O₂,LiFePO₄, Li₂FeP₂O₇, LiMnPO₄, LiFeBO₃, Li₃V₂(PO₄)₃, Li₂CuO₂, LiFeF₃,Li₂FeSiO₄, Li₂MnSiO₄, NMC(Li_(a) (Ni_(x)Mn_(y)Co_(1-x-y))O₂), andNCA(Li(Ni_(x)Co_(y)A_(1-x-y)) O₂). Further, in this embodiment, solidsolutions obtained by substituting some of the atoms in a crystal of anyof these lithium composite metal compounds with another transitionmetal, a typical metal, an alkali metal, an alkaline rare earth element,a lanthanoid, a chalcogenide, a halogen, or the like are also includedin the lithium composite metal compound, and any of these solidsolutions can also be used as the positive electrode active material.

By using the lithium composite metal compound as the active material 2 bin the forming material of the active material section 2, electrontransfer is performed between the particles of the active material 2 b,and lithium ion transfer is performed between the active material 2 band the polymer electrolyte composition 3. According to this, thefunction as the active material section 2 can be favorably exhibited.

The active material section 2 has a bulk density of preferably 50% ormore and 90% or less, more preferably 50% or more and 70% or less. Whenthe active material section 2 has such a bulk density, the surface areaof the inside of the pore of the active material section 2 is enlarged,and the contact area between the active material section 2 and thepolymer electrolyte composition 3 is easily increased. According tothis, in the lithium battery 100, it becomes easier to increase thecapacity than in the related art.

When the above-mentioned bulk density is represented by β(%), theapparent volume including the pores of the active material section 2 isrepresented by v, the mass of the active material section 2 isrepresented by w, and the density of the particles of the activematerial 2 b is represented by ρ, the following numerical formula (x) isestablished. According to this, the bulk density can be determined.β={w/(v·ρ)}×100  (x)

In order to control the bulk density of the active material section 2 tofall within the above range, the average particle diameter (mediandiameter) of the active material 2 b is set to preferably 0.3 μm or moreand 10 μm or less, more preferably 0.5 μm or more and 5 μm or less. Theaverage particle diameter of the active material 2 b can be measured by,for example, dispersing the active material 2 b in n-octyl alcohol at aconcentration of 0.1 mass % or more and 10 mass % or less, anddetermining the median diameter using a light scattering particle sizedistribution analyzer, Nanotrac UPA-EX250 (Nikkiso Co., Ltd.).

The bulk density of the active material section 2 can also be controlledby using a pore forming material in the step of forming the activematerial section 2.

The resistivity of the active material section 2 is preferably 700Ω·cmor less. When the active material section 2 has such a resistivity, inthe lithium battery 100, a sufficient output can be obtained. Theresistivity can be determined by adhering a copper foil as an electrodeto the surface of the active material section 2, and measuring a directcurrent polarization.

In the active material section 2, the plurality of pores communicatewith one another in a mesh-like manner, and therefore, also in the solidportion of the active material section 2, a mesh-like structure isformed. For example, LiCoO₂, which is a positive electrode activematerial, is known to have anisotropy in the electron conductionproperty in a crystal. Due to this, in a structure in which pores extendin a specific direction such that the pores are formed by machining, theelectron conduction property may be decreased depending on the directionof the electron conduction property in a crystal. On the other hand, inthis embodiment, the active material section 2 has a mesh-likestructure, and therefore, a continuous surface which iselectrochemically active regardless of the anisotropy in the electronconduction property or ion conduction property in a crystal can beformed. Due to this, favorable electron conduction can be ensuredregardless of the type of the forming material to be used.

In the active material section 2, the contained amount of the binder(binding agent) for binding the particles of the active material 2 b orthe pore forming material for adjusting the bulk density of the activematerial section 2 is preferably reduced as much as possible. When thebinder or the pore forming material remains in the active materialsection 2 (positive electrode 9), such a component may sometimesadversely affect the electrical characteristics, and therefore, it isnecessary to remove the component by carefully performing heating in apost-process. Specifically, in this embodiment, the percentage loss inmass in the case where the positive electrode 9 is heated at 400° C. for30 minutes is set to 5 mass % or less. The percentage loss in mass ispreferably 3 mass % or less, more preferably 1 mass % or less, andfurther more preferably, the mass loss is not observed or is within thelimits of measurement error. When the percentage loss in mass of thepositive electrode 9 is within such a range, the amount of a solvent oradsorbed water which is evaporated, an organic material which isvaporized by burning or oxidation under a predetermined heatingcondition, or the like is reduced. Accordingly, the electricalcharacteristics (charge/discharge characteristics) of the lithiumbattery 100 can be further improved.

The polymer electrolyte composition 3 contains a polymer electrolyterepresented by the following formula (1) and a lithium salt compound.

In the formula (1), R¹ and R² are each independently hydrogen or CH₃, R³is any of C₂H₄, CH(CH₃)CH₂, and (CH₂)₃, m and n are each acopolymerization ratio of a structural unit in parentheses, and when mand n are set as follows: m+n=10, m and n satisfy the followingformulae: 1≤m≤5 and 5≤n≤9, and p is 2 or more and 8 or less.

The polymer electrolyte represented by the above formula (1) is a((meth)acrylonitrile-polyalkylene glycol (meth)acrylate) copolymercontaining (meth)acrylonitrile and polyalkylene glycol (meth)acrylate asforming materials. In this specification, acrylonitrile andmethacrylonitrile are collectively referred to as “(meth)acrylonitrile”and acrylate and methacrylate are collectively referred to as“(meth)acrylate”, and the same applies also to compounds having asimilar structure.

As shown in the above formula (1), m and n are each a copolymerizationratio (copolymerization molar ratio) of a structural unit inparentheses, and m shows the copolymerization ratio of a structural unitderived from (meth)acrylonitrile, and n shows the copolymerization ratioof a structural unit derived from polyalkylene glycol (meth)acrylate.When m and n are set as follows: m+n=10, m and n satisfy the followingformulae: 1≤m≤5 and 5≤n≤9, preferably 2.5≤m≤5 and 5≤n≤8.5. By settingthe copolymerization molar ratio within the above range, the internalresistance of the polymer electrolyte composition 3 is decreased, andthe ion conduction property can be improved. Further, the solubility ofthe lithium salt compound in the polymer electrolyte can be improved.

As described in the explanatory note to the above formula (1), prepresents the number of repetitions (number of moles) of an alkyleneglycol structure in the polyalkylene glycol (meth)acrylate, and is 2 ormore and 8 or less, preferably 2 or more and 6 or less. By setting thenumber of moles of the polyalkylene glycol structure within the aboverange, the glass transition temperature of the polymer electrolyte isadjusted, and the flexibility can be improved.

As the (meth)acrylonitrile, at least either one of acrylonitrile andmethacrylonitrile is used. By using such (meth)acrylonitrile, a cyanogroup with a relatively large dielectric constant is introduced into thepolymer electrolyte. Therefore, the dielectric constant of the polymerelectrolyte composition is increased, so that the internal resistance ofthe polymer electrolyte composition is decreased, and thus, the ionconduction property is improved.

The polyalkylene glycol (meth)acrylate is not particularly limited aslong as the above formula (1) is satisfied, however, it is morepreferred to use one or more types selected from the group consisting ofpolyethylene glycol acrylate, polypropylene glycol acrylate,polytrimethylene glycol acrylate, polyethylene glycol methacrylate,polypropylene glycol methacrylate, and polytrimethylene glycolmethacrylate. By using such a polyalkylene glycol (meth)acrylate, theflexibility of the polymer electrolyte can be further improved.

The lithium salt compound is not particularly limited, but examplesthereof include lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI),lithium bis(fluorosulfonyl)imide (Li—FSI), lithium hexafluorophosphate(LiPF₆), lithium perchlorate (LiClO₄), lithium tetrafluoroborate(LiBF₄), and lithium hexafluoroarsenate (LiAsF₆). It is possible to useone or more types selected from the above group. By using such a lithiumsalt compound, the ionic activity coefficient in the polymer electrolytecomposition can be further increased.

As the electrolyte of the positive electrode 9, it is preferred to usethe above-mentioned polymer electrolyte composition 3, however, it isalso possible to use any other solid electrolyte. Examples of such othersolid electrolytes include crystalline materials or amorphous materialscontaining an oxide, a sulfide, a halide, a nitride, a hydride, aboride, or the like.

Examples of the solid electrolyte which is an oxide crystalline materialinclude Li_(0.35)La_(0.55)TiO₃, Li_(0.2)La_(0.27)NbO₃, perovskitecrystals or perovskite-like crystals in which some of the elements ofsuch a crystal are substituted with nitrogen (N), fluorine (F), aluminum(Al), strontium (Sr), scandium (Sc) tantalum (Ta), a lanthanoid element,or the like, Li₇La₃Zr₂O₁₂, Li₅La₃Nb₂O₁₂, Li₅BaLa₂TaO₁₂, garnet crystalsor garnet-like crystal in which some of the elements of such a crystalare substituted with nitrogen (N), fluorine (F), aluminum (Al),strontium (Sr), scandium (Sc), tantalum (Ta), a lanthanoid element, orthe like, Li_(1.3)Ti_(1.7)Al_(0.3)(PO₄)₃,Li_(1.4)Al_(0.4)Ti_(1.6)(PO₄)₃, Li_(1.4)Al_(0.4)Ti_(1.4)Ge_(0.2)(P₄)₃,NASICON crystals in which some of the elements of such a crystal aresubstituted with nitrogen (N), fluorine (F), aluminum (Al), strontium(Sr), scandium (Sc), tantalum (Ta), a lanthanoid element, or the like,LISICON crystals such as Li₁₄ZnGe₄O₁₆, Li_(3.4)V_(0.6)Si_(0.4)O₄,Li_(3.6)V_(0.4)Ge_(0.6)O₄, and Li_(2+x)C_(1-x)B_(x)O₃.

Examples of the solid electrolyte which is a sulfide crystallinematerial include Li₁₀GeP₂S₁₂, Li_(9.6)P₃S₁₂,Li_(9.54)Si_(1.74)P_(1.44)S_(11.7)Cl_(0.3), and Li₃PS₄.

Examples of the solid electrolyte which is an amorphous material includeLi₂—TiO₂, La₂O₃—Li₂O—TiO₂, LiNbO₃, LiSO₄, Li₄SiO₄, Li₃PO₄—Li₄SiO₄,Li₄GeO₄—Li₃VO₄, Li₄SiO₄—Li₃VO₄, Li₄GeO₄—Zn₂GeO₂, Li₄SiO₄—LiMoO₄,Li₃PO₄—Li₄SiO₄, Li₄SiO₄—Li₄ZrO₄, SiO₂—P₂O₅—Li₂O, SiO₂—P₂O₅—LiCl,Li₂O—LiCl—B₂O₃, LiI, LiI—CaI₂, LiI—CaO, LiAlCl₄, LiAlF₄, LiF—Al₂O₃,LiBr—Al₂O₃, Li_(2.88)PO_(3.73)N_(0.14), Li₃NI₂, Li₃N—LiI—LiOH,Li₃N—LiCl, Li₆NBr₃, Li₂S—SiS₂—LiI, and Li₂S—SiS₂—P₂ S₅.

Further, among the above-mentioned other solid electrolytes, it ispreferred to use a lithium composite metal compound of the followingformula (2) or (3). By using such a lithium composite metal compound asthe other solid electrolytes, the lithium ion conduction property in thepositive electrode 9 can be improved.(Li_(7-3x+y)Ga_(x))(La_(3-y)Ca_(y))Zr₂O₁₂  (2)(provided that x and y satisfy the following formulae: 0.1≤x≤1 and0.01≤y≤0.5)Li_(7-z)La₃(Zr_(2-z)A_(α))O₁₂  (3)

Provided that z satisfies the following formula: 0.1≤z≤1, A representsat least one type of tantalum (Ta), niobium (Nb), and antimony (Sb), anda satisfies the following formula:0≤α<2.Electrolyte Section

The electrolyte section 20 is provided between the positive electrode 9and the negative electrode 30 as described above. The electrolytesection 20 contains the polymer electrolyte composition 3, but does notcontain the active material 2 b. In the electrolyte section 20, the samepolymer electrolyte composition 3 as in the positive electrode 9described above can be used. By interposing the electrolyte section 20which does not contain the active material 2 b between the positiveelectrode 9 and the negative electrode 30, it becomes difficult toelectrically connect the positive electrode 9 to the negative electrode30, and the occurrence of a short circuit is suppressed.

The thickness of the electrolyte section 20 is preferably 0.1 μm or moreand 100 μm or less, more preferably 0.2 μm or more and 10 μm or less. Bysetting the thickness of the electrolyte section 20 within the aboverange, the internal resistance of the electrolyte section 20 isdecreased, and the occurrence of a short circuit between the positiveelectrode 9 and the negative electrode 30 can be suppressed.

On the one surface 20 a (the surface in contact with the negativeelectrode 30) of the electrolyte section 20, a relief structure such asa trench, a grating, or a pillar may be provided by combining variousmolding methods and processing methods as needed.

As an index of the ion conduction property of the polymer electrolytecomposition 3 and the other solid electrolytes, an ion conductivity canbe adopted. The ion conductivity refers to a bulk conductivity as theconductivity of the electrolyte (solid electrolyte) thereof, a grainboundary conductivity as the conductivity between crystal grains in thecase where the solid electrolyte is a crystalline material, and a totalion conductivity which is the sum of these conductivities. The polymerelectrolyte composition 3 is not a crystalline material, and therefore,the total ion conductivity is equal to the bulk conductivity.

The total ion conductivity of the solid electrolyte is preferably2.0×10⁻⁶ S/cm or more. When the solid electrolyte has such a total ionconductivity, an ion contained in the solid electrolyte at a positionaway from the surface of the active material section 2 easily reachesthe surface of the active material section 2. Due to this, also the ioncan contribute to the battery reaction in the active material section 2,and the capacity of the lithium battery 100 can be further increased.The measurement method for the total ion conductivity will be describedlater.

Method for Producing Battery

A method for producing the lithium battery 100 according to thisembodiment will be described with reference to FIGS. 3, 4A, 4B, 4C, 4D,4E, 4F, and 4G. FIG. 3 is a process flowchart showing a method forproducing the lithium battery. FIGS. 4A to 4G are schematic viewsshowing the method for producing the lithium battery. The process flowshown in FIG. 3 is an example, and the method is not limited thereto.

As shown in FIG. 3, the method for producing the lithium battery 100includes a step S1 of forming an active material section 2 as a moldedbody having a plurality of pores using an active material 2 b, a step S2of preparing a first solution 1X by mixing polyalkylene glycol(meth)acrylate and a lithium salt compound, a step S3 of preparing asecond solution 2X by mixing the first solution 1X and a polymerizationinitiator, a step S4 of preparing a solution 3X containing a precursorof a polymer electrolyte composition 3 (hereinafter also simply referredto as “precursor solution 3X”) by mixing the second solution 2X and(meth)acrylonitrile, a step S5 of bringing the precursor solution 3X ofthe polymer electrolyte composition 3 into contact with the activematerial section 2, a step S6 of forming a positive electrode 9 whichcontains the polymer electrolyte composition 3 and the active materialsection 2 and an electrolyte section 20 which is in contact with thepositive electrode 9 by polymerizing the precursor solution 3X of thepolymer electrolyte composition 3 which is in contact with the activematerial section 2 to form the polymer electrolyte composition 3, a stepS7 of forming a negative electrode 30 so as to be in contact with theelectrolyte section 20, and a step S8 of forming a first currentcollector 41 so as to be in contact with the positive electrode 9.

In the step S1, the active material section 2 is formed using the activematerial 2 b. In this embodiment, as the forming material of the activematerial 2 b, LiCoO₂ which is the lithium composite metal compounddescribed above is used. First, the particles of LiCoO₂ (Sigma-AldrichCo., Ltd.) is subjected to a classification operation in n-butanol usinga wet-type centrifuge model LC-1000 (Krettek Separation GmbH), wherebythe active material 2 b having an average particle diameter of about 5μm is obtained. The melting point of the active material 2 b wasmeasured using Simultaneous Thermal Analyzer TG-DTA/DSC STA8000(PerkinElmer Co., Ltd.), and found to be about 950° C.

Subsequently, the active material 2 b is compression-molded using amolding die 81 (a die with an exhaust port having an inner diameter of10 mm). Specifically, as shown in FIG. 4A, a powder of the activematerial 2 b is filled in the molding die 81 and pressed at a pressureof 624 MPa for 2 minutes. By doing this, a disk-shaped molded material(diameter: 10 mm, thickness: 150 μm) is obtained from LiCoO₂ (activematerial 2 b).

Subsequently, the disk-shaped molded material is fired, whereby theactive material section 2 is formed. As shown in FIG. 4B, thedisk-shaped molded material of the active material 2 b is placed on asubstrate 82 made of magnesium oxide, and subjected to a heatingtreatment at 900° C. for 8 hours, whereby the active material section 2is obtained. The heating treatment temperature is preferably, forexample, 850° C. or higher and lower than the melting point of theactive material 2 b. By this heating treatment, the particles of theactive material 2 b are sintered to one another, and the shape of thedisk-shaped molded material is easily retained. Further, the particlesof the active material 2 b are brought into contact with each other andbound to each other, whereby an electron transfer pathway is formed.

According to this, the particles of the active material 2 b are sinteredto one another, whereby an integrated active material section 2 isobtained. By setting the heating treatment temperature to 850° C. orhigher, sintering proceeds sufficiently, and also the electronconduction property in the crystal of the active material 2 b isensured. By setting the heating treatment temperature lower than themelting point of the active material 2 b, excessive volatilization oflithium ions in the crystal of the active material 2 b is suppressed,and the lithium ion conduction property is maintained. Due to this, itbecomes possible to ensure the electrical capacity of the positiveelectrode 9. The heating treatment temperature is more preferably 875°C. or higher and 950° C. or lower. According to this, in the lithiumbattery 100, an appropriate output and capacity can be provided.

The heating treatment time is preferably set to, for example, 5 minutesor more and 36 hours or less, more preferably 4 hours or more and 14hours or less. By the above-mentioned treatment, the active materialsection 2 having a plurality of pores is obtained. The forming materialof the substrate 82 is not particularly limited, however, it ispreferred to use a material which is less likely to react with theactive material 2 b, the polymer electrolyte composition 3, or the like.As the forming material of the substrate 82, other than magnesium oxide,for example, a single crystal substrate of aluminum oxide, zinc oxide,silicon carbide, or the like can be used.

In the step S2 to the step S4, the precursor solution 3X of the polymerelectrolyte composition 3 is prepared. First, in the step S2,polyalkylene glycol (meth)acrylate and a lithium salt compound aremixed, whereby the first solution 1X is prepared. As the polyalkyleneglycol (meth)acrylate and the lithium salt compound, those describedabove can be used. In this embodiment, as the (meth)acrylonitrile,methacrylonitrile is used, as the polyalkylene glycol (meth)acrylate,polypropylene glycol acrylate (polypropylene glycol monoacrylate)(number average molecular weight Mn: 475, Aldrich Co., Ltd.) is used,and as the lithium salt compound, Li-TFSI is used.

Polypropylene glycol acrylate (hereinafter sometimes abbreviated as“PPGAc”) and Li-TFSI are mixed and stirred. At this time, thedissolution of Li-TFSI in PPGAc may be accelerated by improving thestirring efficiency using an ultrasonic generator 84. Specifically, asshown in FIG. 4C, PPGAc and Li-TFSI are placed in a reagent bottle 83made of PYREX (trademark of Corning Incorporated). The reagent bottle 83is immersed in the ultrasonic generator 84 containing water to applyultrasonic. By doing this, Li-TFSI is dissolved in PPGAc, whereby thefirst solution 1X is obtained.

In the step S3, the first solution 1X and a polymerization initiator aremixed, whereby the second solution 2X is prepared. The polymerizationinitiator is not particularly limited as long as it can initiate thepolymerization reaction at a carbon-carbon double bond included inpolyalkylene glycol (meth)acrylate and (meth)acrylonitrile. Such apolymerization initiator is a compound which generates an active speciessuch as a radical, a cation, or an anion by an energy ray such as lightor heat, and examples thereof include thermal polymerization initiatorssuch as a thermal radical polymerization initiator and a thermalcationic polymerization initiator, and photopolymerization initiatorssuch as a radical photopolymerization initiator, a cationicphotopolymerization initiator, and an anionic photopolymerizationinitiator. That is, as the polymerization initiator, at least one typeof the thermal polymerization initiators and the photopolymerizationinitiators is used.

Examples of the thermal radical polymerization initiator includeazo-based thermal polymerization initiators such as2,2′-azobis(butyronitrile) (AIBN),1,1′-azobis(cyclohexane-1-carbonitrile) (V-40),2,2′-azobis(2,4-dimethylvaleronitrile) (ADVN or AMVN),2,2′-azobis(2-methylbutyronitrile) (AMBN), 4,4′-azobis(4-cyanovalericacid) (ACVA), 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AAPH),2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, and dimethyl2,2′-azobis(2-methylpropionate), peroxide-based thermal polymerizationinitiators such as benzoyl peroxide (BPO), tert-butyl hydroperoxide(TBHP), cumene hydroperoxide, di-tert-butyl peroxide, and dicumylperoxide.

Examples of the thermal cationic polymerization initiator includedicyandiamide, cyclohexyl p-toluenesulfonate, anddiphenyl(methyl)sulfonium tetrafluoroborate.

Examples of the radical photopolymerization initiator includeacetophenone, p-anisyl, benzyl, benzoin, benzophenone, 2-benzoylbenzoate, 4,4′-bis(dimethylamino)benzophenone,4,4′-bis(diethylamino)benzophenone, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, benzoin isobutyl ether, 4-benzoylbenzoate,2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, methyl2-benzoylbenzoate,2-(1,3-benzodioxol-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine, and2,2-dimethoxy-2-phenylacetophenone (trade name “Irgacure 651”, BASF SE).

Examples of the cationic photopolymerization initiator includebis(4-tert-butylphenyl)iodonium hexafluorophosphate,bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate,cyclopropyldiphenylsulfonium tetrafluoroborate, diphenyliodoniumhexafluoroarsenate, diphenyliodonium hexafluorophosphate,diphenyliodonium trifluoromethanesulfonate,2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,triphenylsulfonium tetrafluoroborate, tri-p-tolylsulfoniumhexafluorophosphate, and 4-nitrobenzenediazonium tetrafluoroborate.

Examples of the anionic photopolymerization initiator includeacetophenone O-benzoyloxime, 1,2-bis(4-methoxyphenyl)-2-oxoethylcyclohexylcarbamate nifedipine, 2-nitrobenzyl cyclohexylcarbamate, and2-(9-oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

In this embodiment, in order to form a (methacrylonitrile-PPGAc)copolymer as the polymer electrolyte of the above formula (1) bycopolymerizing methacrylonitrile and PPGAc, a thermal polymerizationreaction is used. Therefore, as the polymerization initiator, AIBN whichis a thermal radical polymerization initiator is used. The method forforming the polymer electrolyte of the above formula (1) is not limitedto the thermal polymerization reaction, and may be a polymerizationreaction using an energy ray such as light, and heat and an energy raymay be used in combination. Therefore, as the above-mentionedpolymerization initiator, one type alone is used or a plurality of typesare used in combination according to the type of the polymerizationreaction to be applied, the types of the polyalkylene glycol(meth)acrylate and the (meth)acrylonitrile, the compositional ratiothereof, or the like.

The first solution 1X and AIBN as the thermal radical polymerizationinitiator are mixed and stirred. At this time, in the same manner as inthe step S2, the dissolution of AIBN in the first solution 1X may beaccelerated by improving the stirring efficiency using the ultrasonicgenerator 84. By doing this, AIBN is completely dissolved in the firstsolution 1X, and the second solution 2X is obtained.

In the step S4, the second solution 2X and methacrylonitrile are mixed,whereby the precursor solution 3X of the polymer electrolyte composition3 is prepared. Specifically, for example, as shown in FIG. 4D, thesecond solution 2X and methacrylonitrile (manufactured by Asahi KaseiCorporation) are placed in a beaker 85 made of PYREX, and a magneticstirring bar 86 is placed therein, and the components are mixed whilestirring by a magnetic stirrer 87. By doing this, the precursor solution3X is obtained.

Here, the molar ratios of methacrylonitrile and PPGAc contained in theprecursor solution 3X are set to be the same as m and n in the aboveformula (1). That is, when m and n are set as follows: m+n=10, m and nsatisfy the following formulae: 1≤m≤5 and 5≤n≤9, preferably 2.5≤m≤5 and5≤n≤8.5. According to this, a (methacrylonitrile-PPGAc) copolymer as thepolymer electrolyte of the above formula (1) can be obtained.

The content of the polymerization initiator contained in the precursorsolution 3X can be appropriately adjusted according to the formulationof the polymer electrolyte or the type of the polymerization initiator.The content of the polymerization initiator is not particularly limited,however, specifically, in the above formula (1), when m and n are set asfollows: m+n=10, the content of the polymerization initiator ispreferably set to 0.02 or more and 0.05 or less in molar ratio. Bysetting the content of the polymerization initiator in the above range,the polymerization reaction (copolymerization) is accelerated, and theamount of unreacted methacrylonitrile or PPGAc in the polymerelectrolyte composition can be reduced.

The content of the lithium salt compound contained in the precursorsolution 3X can be appropriately adjusted according to a desired lithiumion conduction property in the lithium battery 100 or the like. Thecontent of the lithium salt compound is not particularly limited,however, specifically, in the above formula (1), when m and n are set asfollows: m+n=10, the content of the lithium salt compound is preferablyset to 1 or more and 3 or less in molar ratio. By setting the content ofthe lithium salt compound in the above range, the lithium ion conductionproperty in the polymer electrolyte composition is ensured, and thebattery capacity of the lithium battery 100 can be further improved.

In the step S5, the precursor solution 3X and the active materialsection 2 are brought into contact with each other, and the precursorsolution 3X is applied to the active material section 2. Specifically,as shown in FIG. 4E, by using a micropipette 88 for the active materialsection 2 on the substrate 82, the precursor solution 3X is applied tothe surface including the inside of the pores of the active materialsection 2.

As a method for applying the precursor solution 3X, other than droppingusing the micropipette 88, for example, a method such as immersion,spraying, penetration by capillary phenomenon, or spin coating can beused, and these methods may be combined and performed. The precursorsolution 3X has fluidity, and therefore also easily reaches the insideof the pores of the active material section 2. At this time, theprecursor solution 3X is applied so as to wet and spread on the entiresurface including the inside of the pores of the active material section2.

In the step S6, first, the precursor solution 3X brought into contactwith the active material section 2 is heated to cause a polymerizationreaction to form the polymer electrolyte composition 3, whereby thepositive electrode 9 in which the polymer electrolyte composition 3 andthe active material section 2 are assembled is formed. Specifically, asshown in FIG. 4F, the active material section 2 to which the precursorsolution 3X is applied is placed on a hot plate 89 along with thesubstrate 82, and a heating treatment is performed. At this time, as theheating atmosphere, a dry inert gas atmosphere such as argon or N₂ isemployed. It is preferred to employ an atmosphere in which oxygen iscontained as little as possible.

The heating treatment conditions such as the heating treatmenttemperature and time are not particularly limited, and can beappropriately adjusted according to the property of the polymerizationinitiator used in the precursor solution 3X such as a 10-hour half-lifetemperature. The heating treatment conditions are set, for example, asfollows: 60° C. or higher and 90° C. or lower and 30 minutes or more and2 hours or less. By the heating treatment, an active species (radical)is generated from AIBN (thermal radical polymerization initiator)contained in the precursor solution 3X. By this radical, thepolymerization reaction (copolymerization) of methacrylonitrile andPPGAc proceeds, whereby a (methacrylonitrile-PPGAc) copolymer (polymerelectrolyte) is produced. Further, Li-TFSI (lithium salt compound) isdeposited such that it is distributed in the polymer electrolytecomposition 3 as the polymerization reaction proceeds from a state whereit is dissolved in the precursor solution 3X.

Subsequently, the electrolyte section 20 is formed so as to be incontact with the positive electrode 9. In this embodiment, the polymerelectrolyte composition 3 is used as the forming material of theelectrolyte section 20, and therefore, simultaneously with the formationof the positive electrode 9 described above, the electrolyte section 20is formed. Specifically, in the above-mentioned step S5, the activematerial section 2 is sunk in the precursor solution 3X by adjusting theamount of the precursor solution 3X to be dropped onto the activematerial section 2. By performing the heating treatment in the step S6in this state, the electrolyte section 20 in which the active materialsection 2 (active material 2 b) is not contained can be formed on theceiling surface (the surface on which the precursor solution 3X isdropped using the micropipette 88) of the positive electrode 9. Theelectrolyte section 20 is not necessarily formed simultaneously with thepositive electrode 9, and may be separately formed using a known method.

In the step S7, the negative electrode 30 is formed so as to be incontact with the electrolyte section 20. As a method for forming thenegative electrode 30, other than a solution process such as a so-calledsol-gel method or an organometallic thermal decomposition methodinvolving a hydrolysis reaction or the like of an organometalliccompound, a CVD (Chemical Vapor Deposition) method using an appropriatemetal compound and a gas atmosphere, an ALD (Atomic Layer Deposition)method, a green sheet method or a screen printing method using a slurryof solid electrolyte particles, an aerosol deposition method, asputtering method using an appropriate target and a gas atmosphere, aPLD (Pulsed Laser Deposition) method, a vacuum deposition method,plating, thermal spraying, or the like can be used. As the formingmaterial of the negative electrode 30, the above-mentioned negativeelectrode active material can be adopted. In this embodiment, thenegative electrode 30 is formed by depositing lithium (Li metal) havinga thickness of about 3 μm using a vacuum deposition method.

In the step S8, the first current collector 41 is formed so as to be incontact with one surface 9 a of the positive electrode 9. First, asshown in FIG. 4G, a surface facing the surface on which the electrolytesection 20 is formed of the positive electrode 9 is polished under anatmosphere of an inert gas such as N₂. At this time, by polishing, theactive material section 2 is surely exposed to form the one surface 9 a.By doing this, the active material 2 b is electrically connected to thefirst current collector 41. In the case where the active materialsection 2 is sufficiently exposed on the facing surface in theabove-mentioned step, the polishing is omitted, and the facing surfacemay be used as the one surface 9 a.

The polishing method is not particularly limited. For example, for thepolishing, a wrapping film sheet #15000 (manufactured by 3M Company,abrasive grain diameter: 0.3 μm) is used as an abrasive, and the onesurface 9 a is formed by performing a mechanical polishing process.

Subsequently, the first current collector 41 is deposited (formed) onthe one surface 9 a. As a method for forming the first current collector41, an appropriate method can be used according to the reactivity withthe surface on which the first current collector 41 is formed, anelectrical conduction property desired for the electrical circuit, andthe design of the electrical circuit, for example, a method in which anappropriate adhesive layer is separately provided to adhere the firstcurrent collector 41, a gas-phase deposition method such as a PVD(Physical Vapor Deposition) method, a CVD method, a PLD method, an ALDmethod, an aerosol deposition method, or a sputtering method using anappropriate target and a gas atmosphere, a wet method such as a sol-gelmethod, an organometallic thermal decomposition method, or plating, orthe like. Further, as the forming material of the first currentcollector 41, the above-mentioned forming material can be adopted. Inthis embodiment, the first current collector 41 is formed by depositinggold (Au) using a sputtering method. By undergoing the above-mentionedsteps, the lithium battery 100 is produced.

As described above, by the polymer electrolyte, the polymer electrolytecomposition 3, the method for producing the polymer electrolytecomposition 3, the lithium battery 100 as the battery, and the methodfor producing the lithium battery 100 according to the above-mentionedembodiment, the following effects can be obtained.

According to the above-mentioned embodiment, by using the(methacrylonitrile-PPGAc) copolymer which is the polymer electrolyte ofthe above formula (1) in the polymer electrolyte composition 3, thepolymer electrolyte composition 3 having an excellent ion conductionproperty can be provided or produced. Specifically, the polymerelectrolyte composition has a cyano group (nitrile group) with arelatively large dielectric constant, and therefore, the dielectricconstant as the polymer electrolyte composition can be increased. Due tothis, the internal resistance of the polymer electrolyte composition isdecreased, and thus, the ion conduction property is improved. Further,the polymer electrolyte composition has a side chain having apolypropylene glycol structure in addition to a linear carbon mainchain, and therefore, the molecular structure is not bulky as comparedwith, for example, an aromatic ring structure or an aliphatic ringstructure, and the polymer electrolyte composition is rich inflexibility. Therefore, an ion transfer pathway is easily ensured, andthe ion conduction property can be further improved. Therefore, in thelithium battery 100, the lithium ion conduction property is improved,and the battery capacity can be increased.

According to the above-mentioned embodiment, an ion transfer pathway isensured by the (methacrylonitrile-PPGAc) copolymer, and the ionicactivity coefficient of the lithium salt compound is increased. That is,an ion transfer pathway corresponding to the increased ionic activitycoefficient is ensured, and therefore, ionic activation is promoted, andthus, the lithium ion conduction property can be improved. According tothis, the polymer electrolyte composition 3 suitable for the lithiumbattery 100 can be provided.

According to the above-mentioned embodiment, the(methacrylonitrile-PPGAc) copolymer has a low glass transition point andis rich in flexibility as compared with, for example, a(methacrylonitrile-PEGMAc) copolymer or the like, and therefore, byusing the (methacrylonitrile-PPGAc) copolymer in the lithium battery100, the strength against physical stress such as impact can beimproved.

According to the above-mentioned embodiment, the polymer electrolytecomposition 3 containing the polymer electrolyte formed frommethacrylonitrile and PPGAc is formed. That is, the polymer electrolytecomposition 3 having an improved lithium ion conduction property can beproduced. Further, by mixing PPGAc and Li-TFSI as the first solution 1X,the solubility of Li-TFSI can be improved. Therefore, the time requiredfor the step of preparing the precursor solution 3X of the polymerelectrolyte composition 3 is reduced, and the production time for thepolymer electrolyte composition 3 and the lithium battery 100 can bereduced. Further, Li-TFSI can be dispersed in the(methacrylonitrile-PPGAc) copolymer while suppressing unevendistribution therein. According to this, a method for producing thepolymer electrolyte composition 3 and the lithium battery 100, in whichthe lithium ion conduction property is improved, and for which theproduction time can be reduced, can be provided.

According to the above-mentioned embodiment, the polymer electrolytecomposition 3 and the active material section 2 form an assembly, andtherefore, a contact area between the polymer electrolyte composition 3and the active material section 2 is increased to reduce the interfaceimpedance. According to this, a method for producing the lithium battery100 capable of achieving favorable charge transfer at the interfacebetween the polymer electrolyte composition 3 and the active materialsection 2 can be provided.

Next, the effects of the above-mentioned embodiment will be morespecifically described by showing Examples and Comparative Examples withrespect to the lithium battery 100 according to the above-mentionedembodiment. FIG. 5 is a table showing the compositions of polymerelectrolyte compositions according to Examples and Comparative Examples.The weight measurement in the experiment in this specification wasperformed to the first decimal place in mg using an analytical balanceME204T (Mettler Toledo International, Inc.).

Production of Lithium Battery

Example 1

The lithium battery 100 of Example 1 was produced using the productionmethod and the forming materials of the first embodiment describedabove. Here, the procedure from the preparation of a precursor solution3X of a polymer electrolyte composition 3 to the formation of a positiveelectrode 9 and an electrolyte section 20 will be specificallydescribed. As shown in FIG. 5, in the polymer electrolyte composition 3(precursor solution 3X) of Example 1, PPGAc and methacrylonitrile weremixed in equimolar amounts. That is, in the above formula (1), when mand n are set as follows: m+n=10, m and n satisfy the following formula:m=n=5.

In a reagent bottle made of PYREX (volume: 5 mL), PPGAc (1.3870 g,2.92×10⁻³ mol) and Li-TFSI (0.4134 g, 1.44×10⁻³ mol) were weighed andplaced. Here, the amount: 1.44×10⁻³ mol of Li-TFSI corresponds to amolar ratio of about 2.47 when m and n are set as follows: m+n=10 in theabove formula (1). The reagent bottle was immersed in an ultrasonicgenerator containing water, and ultrasonic was applied at roomtemperature for 1.5 hours to dissolve Li-TFSI in PPGAc, whereby a firstsolution 1X was obtained.

AIBN (0.0040 g, 2.42×10⁻⁵ mol) was weighed and added to the firstsolution 1X, and then, the bottle was immersed again in the ultrasonicgenerator, and ultrasonic was applied at room temperature for 15 minutesto completely dissolve AIBN in the first solution 1X, whereby a secondsolution 2X was obtained. Here, the amount: 2.42×10⁻⁵ mol of AIBNcorresponds to a molar ratio of about 0.041 when m and n are set asfollows: m+n=10 in the above formula (1).

Methacrylonitrile (0.1959 g, 2.92×10⁻³ mol) was weighed and added to thesecond solution 2X, and then, a magnetic stirring bar 86 was placedtherein. In this state, stirring was performed at room temperature for15 minutes using a magnetic stirrer 87, whereby a precursor solution 3Xof Example 1 was prepared. In order to accelerate the polymerizationreaction in the precursor solution 3X, the amount of dissolved oxygenmay be reduced by subjecting the precursor solution 3X to a degassingtreatment.

Subsequently, an active material section 2 of LiCoO₂ prepared by themethod described in the first embodiment was placed on a substrate 82(made of magnesium oxide), and the resulting material was placed on ahot plate 89. By using a micropipette 88, 6 μL of the precursor solution3X was dropped from the upper side of the active material section 2. Inthis state, the resulting material was left to stand for 10 minutes, andthereafter, the set temperature of the hot plate 89 was increased to 85°C., and a heating treatment was performed for 1 hour. Thereafter, thetemperature was gradually decreased to room temperature, whereby apositive electrode 9 including an electrolyte section 20 was obtained.The positive electrode 9 including the electrolyte section 20 was usedas a sample for measurement of a lithium ion conductivity (hereinafteralso referred to as “ion conductivity sample”). Further, separately, thelithium battery 100 of Example 1 was produced by applying the productionmethod of the post-process of the first embodiment described above tothe ion conductivity sample.

Example 2

With respect to the lithium battery 100 of Example 2, the same procedureas in Example 1 was performed except that the precursor solution 3X wasprepared using methacrylonitrile (0.0839 g, 1.25×10⁻³ mol), Li-TFSI(0.2957 g, 1.03×10⁻³ mol), and AIBN (0.0028 g, 1.73×10⁻⁵ mol) as shownin FIG. 5 in contrast to Example 1, whereby an ion conductivity sampleand the lithium battery 100 of Example 2 were produced. Therefore, inthe polymer electrolyte (precursor solution 3X) of Example 2, in theabove formula (1), when m and n are set as follows: m+n=10, m and nsatisfy the following formulae: m=3 and n=7, and the molar ratio ofLi-TFSI corresponds to about 1.76, and the molar ratio of AIBNcorresponds to about 0.030.

Example 3

With respect to the lithium battery 100 of Example 3, the same procedureas in Example 1 was performed except that the precursor solution 3X wasprepared using methacrylonitrile (0.0490 g, 7.30×10⁻⁴ mol), Li-TFSI(0.2578 g, 8.98×10⁻⁴ mol), and AIBN (0.0025 g, 1.51×10⁻⁵ mol) as shownin FIG. 5 in contrast to Example 1, whereby an ion conductivity sampleand the lithium battery 100 of Example 3 were produced. Therefore, inthe polymer electrolyte (precursor solution 3X) of Example 3, in theabove formula (1), when m and n are set as follows: m+n=10, m and nsatisfy the following formulae: m=2 and n=8, and the molar ratio ofLi-TFSI corresponds to about 1.54, and the molar ratio of AIBNcorresponds to about 0.026.

Example 4

With respect to the lithium battery 100 of Example 4, the same procedureas in Example 1 was performed except that the precursor solution 3X wasprepared using methacrylonitrile (0.0217 g, 3.24×10⁻⁴ mol), Li-TFSI(0.2288 g, 7.97×10⁻⁴ mol), and AIBN (0.0022 g, 1.34×10⁻⁵ mol) as shownin FIG. 5 in contrast to Example 1, whereby an ion conductivity sampleand the lithium battery 100 of Example 4 were produced. Therefore, inthe polymer electrolyte (precursor solution 3X) of Example 4, in theabove formula (1), when m and n are set as follows: m+n=10, m and nsatisfy the following formulae: m=1 and n=9, and the molar ratio ofLi-TFSI corresponds to about 1.36, and the molar ratio of AIBNcorresponds to about 0.023.

Comparative Example 1

With respect to a lithium battery of Comparative Example 1, the sameprocedure as in Example 1 was performed except that a precursor solutionwas prepared by setting the amount of methacrylonitrile to 0.0000 g,that is, without blending methacrylonitrile, and using Li-TFSI (0.2061g, 7.18×10⁻⁴ mol) and AIBN (0.0020 g, 1.21×10⁻⁵ mol) as shown in FIG. 5in contrast to Example 1, whereby an ion conductivity sample and thelithium battery of Comparative Example 1 were produced. Therefore, inthe polymer electrolyte (precursor solution) in Comparative Example 1,in the above formula (1), when m and n are set as follows: m+n=10, m andn satisfy the following formulae: m=0 and n=10, and the molar ratio ofLi-TFSI corresponds to about 1.23, and the molar ratio of AIBNcorresponds to about 0.021. The polymer electrolyte composition ofComparative Example 1 does not satisfy the following formula: 1≤m≤5.

Comparative Example 2

With respect to a lithium battery of Comparative Example 2,methacrylonitrile (0.2395 g, 3.57×10⁻³ mol), Li-TFSI (0.4593 g,1.60×10⁻³ mol), and AIBN (0.0044 g, 2.69×10⁻⁵ mol) were used as shown inFIG. 5 in contrast to Example 1, however, Li-TFSI was not dissolved inPPGAc, and a precursor solution could not be prepared. In theformulation of the polymer electrolyte of Comparative Example 2, in theabove formula (1), when m and n are set as follows: m+n=10, m and nsatisfy the following formulae: m=5.5 and n=4.5, and the molar ratio ofLi-TFSI corresponds to about 2.73, and the molar ratio of AIBNcorresponds to about 0.046. The polymer electrolyte composition ofComparative Example 2 does not satisfy the following formulae: 1≤m≤5 and5≤n≤9.

Evaluation Methods and Evaluation Results

With respect to the ion conductivity samples and the lithium batteriesof Examples and Comparative Examples, evaluation was performed by thefollowing methods, and the results are shown in FIG. 6. FIG. 6 is atable showing the evaluation results of the lithium ion conductionproperty according to Examples and Comparative Examples.

Lithium Ion Conduction Property

A lithium foil having a diameter of 7 mm and a thickness of 50 μm waspressed against both front and back surfaces of each ion conductivitysample to form an electrode, and further, a copper foil having adiameter of 7 mm and a thickness of 30 μm was pressed against bothsurfaces of the electrode to form a sample for measurement.Subsequently, by using an impedance analyzer SI 1260 (Solartron, Inc.),the AC impedance of the sample for measurement was measured at an ACvoltage amplitude of 10 mV and a measurement frequency ranging from 10⁷Hz to 10⁻² Hz. From a Cole-Cole plot which is the obtained impedancespectrum, the total ion conductivity was calculated as the index of thelithium ion conduction property. The total ion conductivity of each ofthe ion conductivity samples of Examples and Comparative Examples isshown in FIG. 6. Further, the total ion conductivity was evaluatedaccording to the following criteria. The results are shown in FIG. 6.

A: The total ion conductivity is 7.0×10⁻⁶ or more.

B: The total ion conductivity is 2.0×10⁻⁶ or more and less than7.0×10⁻⁶.

C: The total ion conductivity is 7.0×10⁻⁷ or more and less than2.0×10⁻⁶.

D: The total ion conductivity is less than 7.0×10⁻⁷.

As shown in FIG. 6, Examples 1 to 4 were evaluated as A whichcorresponds to “very suitable”. According to this, it was shown thatExamples 1 to 4 have an excellent lithium ion conduction property.

On the other hand, Comparative Example 1 was evaluated as C whichcorresponds to “not suitable”, and therefore, it was found thatComparative Example 1 has a lower lithium ion conduction property thanExamples. Further, it was found that in Comparative Example 2, a lithiumbattery could not be produced.

Charge/Discharge Capacity

With respect to the lithium batteries 100 of Example 1 and ComparativeExample 1, charge and discharge were performed at a charge/dischargerate of 0.1 C in an environment at 25° C. As a result, in both of thelithium battery 100 of Example 1 and the lithium battery of ComparativeExample 1, a plateau of a charge curve was observed at 3.9 V. Thispotential was equal to the potential of the desorption reaction oflithium of HT (high-temperature phase)-LiCoO₂.

Further, with respect to the lithium batteries 100 of Example 1 andComparative Example 1, a charge/discharge capacity in the case wherecharge and discharge were repeated was measured. Specifically, aninitial charge/discharge capacity and a charge/discharge capacity afterrepeating 100 cycles of charge and discharge were measured, and adischarge capacity maintenance rate after 100 cycles of charge anddischarge was calculated. The theoretical capacity (the withdrawalamount of lithium atoms in the composition of LiCoO₂) is 137 mAh/g.

As a result of the above evaluation, it was found that in the lithiumbattery 100 of Example 1, 80% (110 mAh/g) of the above-mentionedtheoretical capacity (137 mAh/g) can be ensured. Further, it was foundthat the discharge capacity maintenance rate after repeating 100 cyclesof charge and discharge can be maintained at 90% (99 mAh/g). Theseresults showed that the lithium battery 100 of Example 1 has a stablecycle property.

On the other hand, in the configuration of Comparative Example 1, theinitial resistance was too high, and it did not function as a battery.

Second Embodiment

Method for Producing Battery

A method for producing a lithium battery 200 according to thisembodiment will be described with reference to FIGS. 7, 8A, 8B, 8C, and8D. FIG. 7 is a process flowchart showing a method for producing alithium battery as a battery according to the second embodiment. FIGS.8A to 8D are schematic views showing the method for producing thelithium battery. Incidentally, the same reference numerals are used forthe same constituent components as those of the first embodiment, and arepetitive description will be omitted. The process flow shown in FIG. 7is an example, and the method is not limited thereto.

As shown in FIG. 7, the method for producing the lithium battery 200 ofthis embodiment includes a step S11 of preparing a first solution 21X bymixing polyalkylene glycol (meth)acrylate and a lithium salt compound, astep S12 of preparing a second solution 22X by mixing the first solution21X and a polymerization initiator, a step S13 of preparing a precursorsolution 23X of a polymer electrolyte composition 23 by mixing thesecond solution 22X and (meth)acrylonitrile, a step S14 of preparing amixture 24X containing (meth)acrylonitrile, polyalkylene glycol(meth)acrylate, a lithium salt compound, a polymerization initiator, andan active material 2 b in the form of particles by mixing the precursorsolution 23X and the active material 2 b in the form of particles, astep S15 of forming a molded material 24Y in the form of a sheet usingthe mixture 24X, a step S16 of forming an assembly 24 containing theactive material 2 b and the polymer electrolyte composition 23 obtainedby polymerization of (meth)acrylonitrile and polyalkylene glycol(meth)acrylate using the molded material 24Y, a step S17 of forming anelectrolyte section 220 so as to be in contact with the assembly 24, astep S18 of forming a negative electrode 230 so as to be in contact withthe electrolyte section 220, and a step S19 of forming a first currentcollector 241 so as to be in contact with the assembly 24.

As described above, the method for producing the lithium battery 200according to the second embodiment is different from the firstembodiment in that the assembly 24 is directly formed from the mixture24X using a so-called green sheet molding method without forming theactive material section 2 as in the first embodiment.

The step S11 to the step S13 are performed in the same manner as thestep S2 to the step S4 in the first embodiment, whereby the precursorsolution 23X is prepared. As the forming materials and devices used inthe step S11 to the step S13, the same forming materials and devices asin the first embodiment can be applied, and therefore, a detaileddescription thereof will be omitted. In this embodiment, the precursorsolution 23X is prepared using the same forming materials as in thefirst embodiment except that polyethylene glycol methacrylate (numberaverage molecular weight Mn: 360, Aldrich Co., Ltd.) (hereinaftersometimes abbreviated as “PEGMAc”) is used as the polyalkylene glycol(meth)acrylate.

In the step S14, the precursor solution 23X and the active material 2 bin the form of particles are mixed, whereby the mixture 24X in the formof a slurry is prepared. As the active material 2 b, the particles ofLiCoO₂ (Sigma-Aldrich Co., Ltd.) subjected to a classification operationso as to have an average particle diameter of about 5 μm are used in thesame manner as in the first embodiment.

The mixture 24X preferably contains a conductive additive 27. By addingthe conductive additive 27, the electron conduction property of theassembly 24 can be improved. Examples of the forming material of theconductive additive 27 include conductive polymer compounds such aspolythiophene, polyacetylene, polypyrrole, polyaniline, andpoly(para-phenylene), each doped with a carrier such as a conductiveion, carbon fibers such as a PAN (polyacrylonitrile)-based orpitch-based carbon fiber, conductive carbon blacks, materials obtainedby coating a glass fiber, a carbon fiber, or the like with a metal suchas nickel (Ni) or Al (aluminum), metals or metalloids such as silicon(Si), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), yttrium(Y), zirconium (Zr), neodymium (Nd), molybdenum(Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), hafnium(Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium(Ir), a lanthanoid, platinum (Pt), gold (Au), stainless steel, andbrass, and oxides such as In₂O₃, SnO₂, Fe₂O₃, CoO, ZnO, and RuO₂. Inthis embodiment, as the conductive additive, Ketchen black (averageparticle diameter: about 100 nm, Lion Specialty Chemicals Co., Ltd.)which is a conductive carbon black is added. Incidentally, in the firstembodiment, the active material section 2 in which the particles of theactive material 2 b are connected to each other is formed, andtherefore, the electron conduction property is easily ensured, and thus,it is not necessary to use the conductive additive 27.

First, the precursor solution 23X, the active material 2 b, and Ketchenblack are weighed and placed in a 50-mL bottle made of PYREX. At thistime, the amount of the active material 2 b is set to 90 parts by massto 95 parts by mass, the amount of the conductive additive 27 (Ketchenblack) is set to 5 parts by mass to 10 parts by mass, so that the totalamount of the active material 2 b and the conductive additive 27 is setto 100 parts by mass, and the amount of the precursor solution 23X isset to 50 parts by mass to 200 parts by mass. Subsequently, a magneticstirring bar 86 is placed in the above-mentioned 50-mL bottle, and thecomponents are mixed while stirring using a magnetic stirrer 87. Bydoing this, the mixture 24X is obtained.

In the step S15, the molded material 24Y in the form of a sheet isformed using the mixture 24X. As shown in FIG. 8A, the mixture 24X iscoated on a substrate 92 using a doctor blade molding machine 91 as acoating machine, whereby the molded material 24Y in the form of a sheetis formed. Here, the coating thickness of the molded material 24Y isadjusted so that the thickness of the below-mentioned assembly 24 is 20μm to 100 μm. Incidentally, by setting the thickness of the substrate 92to about 0.1 mm, and using the same forming material as that of thefirst current collector 41 described above for the substrate 92, thesubstrate 92 can be applied as the below-mentioned first currentcollector 241.

In the step S16, the assembly 24 as the positive electrode containingthe polymer electrolyte composition 23 obtained by polymerization ofmethacrylonitrile and PEGMAc, the active material 2 b, and theconductive additive 27 is formed from the molded material 24Y. As shownin FIG. 8B, the substrate 92 and the molded material 24Y are subjectedto a heating treatment at 90° C. for about 1 hour. The heatingatmosphere is set in the same manner as in the first embodiment.

A polymerization reaction (copolymerization) of methacrylonitrile andPEGMAc proceeds by an active species generated from AIBN contained inthe mixture 24X by the heating treatment. By this reaction, a(methacrylonitrile-PEGMAc) copolymer as the polymer electrolyte of theabove formula (1) is produced. Further, Li-TFSI (lithium salt compound)is deposited as the polymerization reaction proceeds from a state whereit is dissolved in the mixture 24X, and forms the polymer electrolytecomposition 23 along with the polymer electrolyte. The active material 2b and the conductive additive 27 are distributed in the form of islandswhile coming into contact with each other, and the polymer electrolytecomposition 23 is formed in a gap between the islands. By doing this,the assembly 24 of the active material 2 b, the conductive additive 27,and the polymer electrolyte composition 23 is obtained. Thereafter, theassembly 24 in the form of a sheet is cut out in the shape of a disk(diameter: about 10 mm) along with the substrate 92. The substrate 92 isused as the first current collector 241. In the case where the substrate92 is not used as the first current collector 241, after the substrate92 is detached from the assembly 24, the first current collector 241 isprovided in the same manner as the first current collector 41 of thefirst embodiment in the step S19.

In the step S17, the electrolyte section 220 (see FIG. 8D) is formed soas to be in contact with the assembly 24. As the forming material of theelectrolyte section 220, the polymer electrolyte composition 23 is used.As shown in FIG. 8C, in the same manner as the application of theprecursor solution 3X in the first embodiment, the precursor solution23X is applied onto the upper surface (the surface on the opposite sideto the surface on which the first current collector 241 is formed) ofthe assembly 24, followed by a heating treatment, whereby theelectrolyte section 220 is formed. By adjusting the contents of theactive material 2 b and the conductive additive 27 in the mixture 24X, alayer (electrolyte section 220) which does not contain the activematerial 2 b and the conductive additive 27 may be formed on the ceilingsurface of the assembly 24 simultaneously with the assembly 24 in thestep S16.

In the step S18, the negative electrode 230 is formed so as to be incontact with the electrolyte section 220. The negative electrode 230 canbe formed using the same forming material and the same method as thosefor the negative electrode 30 of the first embodiment. The formation ofthe first current collector 241 in the step S19 can be performed in thestep S16 as described above, and therefore, the description thereof willbe omitted. By the above-mentioned steps, the lithium battery 200 shownin FIG. 8D is produced.

As described above, by the polymer electrolyte, the polymer electrolytecomposition 23, the method for producing the polymer electrolytecomposition 23, the lithium battery 200 as the battery, and the methodfor producing the lithium battery 200 according to the above-mentionedembodiment, the following effects can be obtained in addition to theeffects of the first embodiment.

According to the above-mentioned embodiment, the lithium battery 200containing the (methacrylonitrile-PEGMAc) copolymer which is the polymerelectrolyte and Li-TFSI (lithium salt compound) as the polymerelectrolyte composition 23, and having an improved lithium ionconduction property can be produced. Further, since the conductiveadditive 27 is used, an electron conduction property can be ensuredwithout forming the active material section 2 of the active material 2 bas in the first embodiment. Further, since the assembly 24 containingthe polymer electrolyte composition 23 and the active material 2 b isdirectly formed, the production steps of the lithium battery 200 can besimplified.

Next, the effects of the above-mentioned embodiment will be morespecifically described by showing Examples with respect to the lithiumbattery 200 according to the above-mentioned embodiment.

Production of Lithium Battery

Example 5

The lithium battery 200 of Example 5 was produced using the productionmethod and the forming materials of the second embodiment describedabove. Here, the procedure from the preparation of a precursor solution23X of a polymer electrolyte composition 23 to the formation of anassembly 24 and an electrolyte section 220 will be specificallydescribed.

With respect to the lithium battery 200 of Example 5, the precursorsolution 23X of Example 5 was prepared in the same manner as in Example1 of the first embodiment except that PEGMAc (13.8700 g, 3.85×10⁻² mol),methacrylonitrile (0.8386 g, 1.25×10⁻² mol), Li-TFSI (2.9570 g,1.03×10⁻² mol), and AIBN (0.0280 g, 1.73×10⁻⁴ mol) were used, and areagent bottle made of PYREX (volume: 50 mL) was used in the preparationin contrast to Example 1. In the polymer electrolyte (precursor solution23X) in Example 5, in the above formula (1), when m and n are set asfollows: m+n=10, m and n satisfy the following formulae: m=3 and n=7,and the molar ratio of Li-TFSI corresponds to about 1.76, and the molarratio of AIBN corresponds to about 0.030.

Subsequently, the precursor solution 23X (6.5000 g), LiCoO₂ particles(9.5000 g), and Ketchen black (0.5000 g) were weighed and placed in areagent bottle made of PYREX (volume: 50 mL). Further, a magneticstirring bar 86 was placed therein, and stirring was performed at roomtemperature for 15 minutes using a magnetic stirrer 87, whereby amixture 24X in the form of a slurry was prepared.

Subsequently, a molded material 24Y in the form of a sheet was formedfrom the mixture 24X using a doctor blade molding machine 91 and analuminum plate having a thickness of 0.1 mm as a substrate 92.Thereafter, the molded material 24Y was subjected to a heating treatmentat 90° C. for 1 hour in a dry N₂ gas atmosphere, whereby an assembly 24containing a (methacrylonitrile-PEGMAc) copolymer as the polymerelectrolyte was formed. The assembly 24 was cut out in the shape of adisk (diameter: about 10 mm, thickness: about 150 μm) along with thealuminum plate to be used as a first current collector 241. Further, anegative electrode 230 was formed in the same manner as in the firstembodiment, whereby the lithium battery 200 of Example 5 was produced.

Evaluation for Lithium Battery

With respect to the lithium battery 200 of Example 5, the sameevaluation as in Example 1 of the first embodiment was performed. As aresult, it was confirmed that the lithium battery 200 of Example 5 hasequivalent performance to that of Example 1 in terms of charge/dischargecapacity and discharge capacity maintenance rate.

Third Embodiment

Battery

First, a battery according to this embodiment will be described withreference to FIG. 9. In this embodiment, a lithium battery will bedescribed as an example of the battery. FIG. 9 is a schematicperspective view showing a configuration of a lithium battery as thebattery according to the third embodiment. Incidentally, the samereference numerals are used for the same constituent components as thoseof the first embodiment, and a repetitive description will be omitted.

As shown in FIG. 9, a lithium battery 300 of this embodiment includes anelectrolyte section 320 which contains a polymer electrolyte composition33, a positive electrode 39 as an assembly which is provided in contactwith the electrolyte section 320 and contains an active material 2 b andan electrolyte 34, a negative electrode 30 which is provided for thepositive electrode 39 through the electrolyte section 320, and a firstcurrent collector 41 which is provided for the electrolyte section 320through the positive electrode 39. The active material 2 b forms theactive material section 2 in the same manner as in the first embodiment.

The lithium battery 300 is different from the lithium battery 100 of thefirst embodiment in that the polymer electrolyte of the above formula(1) is not contained in the positive electrode 39. That is, in thelithium battery 300, as the forming material of the electrolyte section320, the polymer electrolyte composition 33 containing the polymerelectrolyte is used, and as the forming material of the electrolyte 34contained in the positive electrode 39, a solid electrolyte other thanthe polymer electrolyte composition 33 is used.

In the lithium battery 300, for the negative electrode 30, the firstcurrent collector 41, and the active material section 2 composed of theactive material 2 b, the same forming materials as in the firstembodiment are used. As the forming material of the electrolyte 34contained in the positive electrode 39, any other solid electrolyteincluding a crystalline material or an amorphous material containing anoxide, a sulfide, a halide, a nitride, a hydride, a boride, or the likeexemplified in the first embodiment is used.

The polymer electrolyte composition 33 contains the polymer electrolyteof the above formula (1) and a lithium salt compound in the same manneras in the first embodiment. As the polymer electrolyte and the lithiumsalt compound, the compounds exemplified in the first embodiment can beadopted.

Method for Producing Battery

A method for producing the lithium battery 300 according to thisembodiment will be described with reference to FIGS. 10 and 11. FIG. 10is a process flowchart showing a method for producing the lithiumbattery. FIG. 11 is a schematic view showing the method for producingthe lithium battery.

As shown in FIG. 10, the method for producing the lithium battery 300includes a step S21 of forming a positive electrode 39 as an assemblycontaining an active material 2 b and an electrolyte 34, a step S22 ofpreparing a precursor solution 33X of a polymer electrolyte composition33 containing (meth)acrylonitrile, polyalkylene glycol (meth)acrylate, alithium salt compound, and a polymerization initiator, a step S23 ofbringing the precursor solution 33X into contact with the positiveelectrode 39, a step S24 of forming an electrolyte section 320containing the polymer electrolyte composition 33 so as to be in contactwith the positive electrode 39 by polymerizing the precursor solution33X, a step S25 of forming a negative electrode 30 so as to be incontact with the electrolyte section 320, and a step S26 of forming afirst current collector 41 for the electrolyte section 320 through thepositive electrode 39.

In the step S21, the active material section 2 is formed using theactive material 2 b, and the active material section 2 and theelectrolyte 34 are assembled to form the positive electrode 39. As amethod for forming the active material section 2, the same method as thestep S1 of the first embodiment can be adopted.

In order to assemble the electrolyte 34 and the active material section2, first, a solution 34X containing a precursor of the electrolyte 34(hereinafter also simply referred to as “precursor solution 34X”) isprepared. As the precursor solution 34X, at least one type of thefollowing (a), (b), (c), and (d) can be used. Among these, (b) is aprecursor in the case where a solid electrolyte is formed using asol-gel method.

(a) a composition having a salt which contains a metal atom included ina solid electrolyte at a proportion according to the compositionalformula of the solid electrolyte and is converted into the solidelectrolyte by oxidation

(b) a composition having a metal alkoxide compound which contains ametal atom included in a solid electrolyte at a proportion according tothe compositional formula of the solid electrolyte

(c) a dispersion liquid in which a microparticle of a solid electrolyteor a microparticle sol containing a metal atom included in a solidelectrolyte at a proportion according to the compositional formula ofthe solid electrolyte is dispersed in a solvent

(d) a composition having a salt which contains a metal atom included ina solid electrolyte at a proportion according to the compositionalformula of the solid electrolyte and is converted into the solidelectrolyte by oxidation and having a metal alkoxide compound

Subsequently, particles of the electrolyte 34 are prepared from theprecursor solution 34X. The above-mentioned solution is heated and firedat 800° C. over 10 hours in pressurized dry air, whereby a solidmaterial is prepared. Subsequently, this solid material is pulverizedand classified, whereby particles of the electrolyte 34 having anaverage particle diameter of about 0.5 μm are obtained.

Subsequently, a melt of the particles of the electrolyte 34 is broughtinto contact with the active material section 2, whereby the electrolyte34 is provided (formed) inside the pores of the active material section2. First, the particles of the electrolyte 34 are placed above theactive material section 2, and the particles of the electrolyte 34 areheated. The heating conditions are preferably such that heating isperformed at a temperature of 800° C. or higher and 1000° C. or lowerfor 1 minute to 240 minutes. Further, the heating is preferablyperformed in dry air.

By heating the particles of the electrolyte 34 at a temperatureexceeding the melting point thereof, the particles of the electrolyte 34are melted to become a melt. The melt covers the entire active materialsection 2 while penetrating into the inside of the pores of the activematerial section 2 from the upper surface of the active material section2. As a method for heating the particles of the electrolyte 34, laserannealing may be used.

Here, the method for forming the electrolyte 34 in the positiveelectrode 39 is not limited to the above-mentioned method in which themelt of the particles of the electrolyte 34 is allowed to penetrate.Examples of other forming methods include immersion, dropping, spraying,penetration by capillary phenomenon, and spin coating using theprecursor solution 34X, and by performing a heating treatment in apost-process, removal of the solvent in the solution and firing of theelectrolyte 34 may be performed. Further, after providing the particlesof the electrolyte 34 in the pores of the active material section 2, theelectrolyte 34 may be formed by a heating treatment. Thereafter, theactive material section 2 is left to cool so as to assemble the activematerial section 2 and the electrolyte 34, whereby the positiveelectrode 39 is formed. Incidentally, the method for forming thepositive electrode 39 is not limited to the above-mentioned method, andfor example, the positive electrode 39 may be formed using a green sheetmolding method described in the second embodiment.

In the step S22, the precursor solution 33X of the polymer electrolytecomposition 33 containing (meth)acrylonitrile, polyalkylene glycol(meth)acrylate, a lithium salt compound, and a polymerization initiatoris prepared. The step S22 is performed in the same manner as in the stepS2 to the step S4 of the first embodiment. Here, in this embodiment, theformation of the polymer electrolyte (polymerization reaction) isperformed by irradiation with a UV ray (energy ray), and therefore,among the above-mentioned polymerization initiators, at least any of aradical photopolymerization initiator, a cationic photopolymerizationinitiator, and an anionic photopolymerization initiator is used.

In the step S23, the precursor solution 33X is brought into contact withthe positive electrode 39, whereby the precursor solution 33X is appliedto the positive electrode 39. Specifically, in the same manner as in thestep S5 (see FIG. 4E) of the first embodiment, the precursor solution33X is applied onto the ceiling surface of the positive electrode 39placed on the substrate 82 using the micropipette 88. At this time, theprecursor solution 33X may be applied in an amount sufficient forforming the electrolyte section 320.

As the method for applying the precursor solution 33X, other thandropping using the micropipette 88, for example, a method such asimmersion, spraying, penetration by capillary phenomenon, or spincoating can be used, and these methods may be combined and performed.

In the step S24, the electrolyte section 320 containing the polymerelectrolyte composition 33 is formed so as to be in contact with thepositive electrode 39 by polymerizing the precursor solution 33X. Inthis embodiment, a polymerization reaction of (meth)acrylonitrile andpolyalkylene glycol (meth)acrylate is performed by UV irradiation.Therefore, as shown in FIG. 11, the precursor solution 33X applied tothe positive electrode 39 is irradiated with a UV (Ultraviolet) ray froma UV irradiation device 93.

As a light source (UV light generation system) in the UV irradiationdevice 93, for example, a mercury lamp, a metal halide lamp, a UVlight-emitting diode (UV-LED), a UV laser diode (UV-LD), or the like canbe used.

The wavelength of the light source can be set according to theabsorption wavelength of the polymerization initiator or the like, andis not limited, however, the emission peak wavelength of the lightsource is preferably, for example, in the range of 200 nm to 400 nm. Theemission peak wavelength refers to a wavelength at which the lightemission intensity becomes the maximum. It is preferred to irradiate aUV ray having the above emission peak wavelength at an irradiationenergy of 50 mJ/cm² or more and 400 mJ/cm² or less.

The UV irradiation time for the precursor solution 33X can beappropriately adjusted according to the irradiation energy of the UV rayto be irradiated, the type of the polymerization initiator, thethickness of the electrolyte section 320 to be formed, or the like. TheUV irradiation time is not particularly limited, but can be set to, forexample, 30 seconds or more and 1 hour or less.

By performing the polymerization reaction under the above-mentionedconditions, the forming time of the polymer electrolyte can be reducedas compared with a thermal polymerization reaction. Due to this, theproduction time for the lithium battery 300 can be reduced. The methodfor forming the electrolyte section 320 containing the polymerelectrolyte composition 33 is not limited to the above-mentioned method,and a thermal polymerization reaction may be used, and a polymerizationreaction by an energy ray and a thermal polymerization reaction may beused in combination.

The step S25 (formation of the negative electrode 30) and the step S26(formation of the first current collector 41) correspond to the step S7and the step S8, respectively, of the first embodiment, and thereforeare performed in the same manner as in the first embodiment. Byundergoing the above-mentioned steps, the lithium battery 300 isproduced.

As described above, by the lithium battery 300 as the battery and themethod for producing the lithium battery 300 according to theabove-mentioned embodiment, the following effects can be obtained inaddition to the effects of the first embodiment.

According to the above-mentioned embodiment, a polymerization reactionby an energy ray is used in the formation of the electrolyte section320, and therefore, the formation can be performed in a shorter timethan in the case where a thermal polymerization reaction or a methodsuch as firing is used, and the production time for the lithium battery300 can be reduced. Further, the electrolyte section 320 is formed so asto contain a ((meth)acrylonitrile-polyalkylene glycol (meth)acrylate)copolymer and a lithium salt compound, and therefore, the lithiumbattery 300 in which the lithium ion conduction property of theelectrolyte section 320 is improved as compared with the related art canbe produced.

Next, the effects of the above-mentioned embodiment will be morespecifically described by showing Examples and Comparative Examples withrespect to the electrolyte section 320 to be used in the lithium battery300 according to the above-mentioned embodiment. FIGS. 12 and 13 aretables showing the compositions of polymer electrolyte compositionsaccording to Examples and Comparative Examples.

Production of Electrolyte Section for Evaluation

Example 6

An electrolyte section for evaluation of Example 6 was produced usingthe production method of the third embodiment described above. Here, amethod for producing the electrolyte section for evaluation alone willbe specifically described.

The polymer electrolyte composition 33 (electrolyte section forevaluation) of Example 6 contains the polymer electrolyte of the aboveformula (1) obtained by using acrylonitrile (manufactured by Asahi KaseiCorporation) as the (meth)acrylonitrile and PPGAc as the formingmaterials, Li-TFSI (lithium salt compound), and Irgacure 651 (radicalphotopolymerization initiator) as shown in FIG. 12.

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 6 was prepared in the same manner as in Example 1 except thatmethacrylonitrile of Example 1 was changed to acrylonitrile (0.1549 g,2.92×10⁻³ mol) and AIBN (polymerization initiator) of Example 1 waschanged to Irgacure 651 (polymerization initiator) (0.0062 g, 2.42×10⁻⁵mol). Incidentally, in the polymer electrolyte composition 33 (precursorsolution 33X) of Example 6, in the above formula (1), when m and n areset as follows: m+n=10, m and n satisfy the following formula: m=n=5.

Subsequently, 20 μL of the precursor solution 33X was dropped using amicropipette approximately at the center in the long side direction on amicroscope slide, white, ground edges, No. 2 (product No. S1112,Matsunami Glass Ind., Ltd.). Subsequently, an NEO cover glass (25 mm×36mm) No. 1 (Matsunami Glass Ind., Ltd.) having a thickness of about 0.15mm was placed as a spacer in the vicinity of each of the both ends inthe long side direction of the microscope slide one by one. Further, amicroscope slide, white, ground edges, No. 2 was overlaid on the uppersurface thereof, and a region in the vicinity of each of the both endsin the long side direction of the resulting material was held with adouble clip. By doing this, the dropped precursor solution 33X wasformed into a liquid film having a thickness of about 0.15 mm betweenthe above-mentioned microscope slides.

Subsequently, by using a handy UV lamp (short wavelength 254 nm type)(manufactured by AS ONE Co., Ltd.) having an emission peak wavelength of254 nm as the UV irradiation device 93, the liquid film of the precursorsolution 33X was irradiated with a UV ray for 30 minutes from asubstantially vertical direction. By doing this, the polymerizationreaction proceeds, whereby the precursor solution 33X was cured.Thereafter, a razor blade was inserted between the two microscope slidesto separate the microscope slides, and a film formed by curing theprecursor solution 33X was peeled off from the microscope slides. Thefilm formed by curing the precursor solution 33X was used as theelectrolyte section for evaluation of Example 6.

Example 7

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 7 was prepared in the same manner as in Example 2 except thatmethacrylonitrile of Example 2 was changed to acrylonitrile (0.0663 g,1.25×10⁻³ mol) and AIBN (polymerization initiator) of Example 2 waschanged to Irgacure 651 (polymerization initiator) (0.0044 g, 1.73×10⁻⁵mol). Incidentally, in the polymer electrolyte composition 33 (precursorsolution 33X) of Example 7, in the above formula (1), when m and n areset as follows: m+n=10, m and n satisfy the following formulae: m=3 andn=7. Thereafter, the same procedure as in Example 6 was performed,whereby an electrolyte section for evaluation was produced.

Example 8

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 8 was prepared in the same manner as in Example 3 except thatmethacrylonitrile of Example 3 was changed to acrylonitrile (0.0387 g,7.30×10⁻⁴ mol) and AIBN (polymerization initiator) of Example 3 waschanged to Irgacure 651 (polymerization initiator) (0.0039 g, 1.51×10⁻⁵mol). Incidentally, in the polymer electrolyte composition 33 (precursorsolution 33X) of Example 8, in the above formula (1), when m and n areset as follows: m+n=10, m and n satisfy the following formulae: m=2 andn=8. Thereafter, the same procedure as in Example 6 was performed,whereby an electrolyte section for evaluation was produced.

Example 9

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 9 was prepared in the same manner as in Example 4 except thatmethacrylonitrile of Example 4 was changed to acrylonitrile (0.0172 g,3.24×10⁻⁴ mol) and AIBN (polymerization initiator) of Example 4 waschanged to Irgacure 651 (polymerization initiator) (0.0034 g, 1.34×10⁻⁵mol). Incidentally, in the polymer electrolyte composition 33 (precursorsolution 33X) of Example 9, in the above formula (1), when m and n areset as follows: m+n=10, m and n satisfy the following formulae: m=1 andn=9. Thereafter, the same procedure as in Example 6 was performed,whereby an electrolyte section for evaluation was produced.

Example 10

The polymer electrolyte composition 33 (electrolyte section forevaluation) of Example 10 contains the polymer electrolyte of the aboveformula (1) obtained by using PEGMAc and methacrylonitrile as theforming materials, Li-TFSI (lithium salt compound), and Irgacure 651(radical photopolymerization initiator) as shown in FIG. 13.

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 10 was prepared in the same manner as in Example 6 except thatPPGAc (polyalkylene glycol (meth)acrylate) of Example 6 was changed toPEGMAc (polyalkylene glycol (meth)acrylate) (1.0512 g, 2.92×10⁻³ mol)and acrylonitrile of Example 6 was changed to methacrylonitrile (0.1959g, 2.92×10⁻³ mol). Incidentally, in the polymer electrolyte composition33 (precursor solution 33X) of Example 10, in the above formula (1),when m and n are set as follows: m+n=10, m and n satisfy the followingformula: m=n=5.

Subsequently, in the same manner as in Example 6, the precursor solution33X was irradiated with a UV ray for 30 minutes using the UV irradiationdevice 93. Thereafter, the double clips holding the two microscopeslides were detached, and the microscope slides were placed on a hotplate pre-heated to 50° C. After a heating treatment was performed for 1minute in this state, the microscope slides were picked up. That is, inExample 10, the electrolyte section for evaluation was formed by usingUV irradiation and a heating treatment in combination. Thereafter, afilm of the cured precursor solution 33X was peeled off in the samemanner as in Example 6. This film was used as the electrolyte sectionfor evaluation of Example 10.

Example 11

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 11 was prepared in the same manner as in Example 7 except thatPPGAc of Example 7 was changed to PEGMAc (1.0512 g, 2.92×10⁻³ mol) andacrylonitrile of Example 7 was changed to methacrylonitrile (0.0839 g,1.25×10⁻³ mol). Incidentally, in the polymer electrolyte composition 33(precursor solution 33X) of Example 11, in the above formula (1), when mand n are set as follows: m+n=10, m and n satisfy the followingformulae: m=3 and n=7. Thereafter, the same procedure as in Example 10was performed, whereby an electrolyte section for evaluation wasproduced.

Example 12

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 12 was prepared in the same manner as in Example 8 except thatPPGAc of Example 8 was changed to PEGMAc (1.0512 g, 2.92×10⁻³ mol) andacrylonitrile of Example 8 was changed to methacrylonitrile (0.0490 g,7.30×10⁻⁴ mol). Incidentally, in the polymer electrolyte composition 33(precursor solution 33X) of Example 12, in the above formula (1), when mand n are set as follows: m+n=10, m and n satisfy the followingformulae: m=2 and n=8. Thereafter, the same procedure as in Example 10was performed, whereby an electrolyte section for evaluation wasproduced.

Example 13

The precursor solution 33X of the polymer electrolyte composition 33 ofExample 13 was prepared in the same manner as in Example 9 except thatPPGAc of Example 9 was changed to PEGMAc (1.0512 g, 2.92×10⁻³ mol) andacrylonitrile of Example 9 was changed to methacrylonitrile (0.0217 g,3.24×10⁻⁴ mol). Incidentally, in the polymer electrolyte composition 33(precursor solution 33X) of Example 13, in the above formula (1), when mand n are set as follows: m+n=10, m and n satisfy the followingformulae: m=1 and n=9. Thereafter, the same procedure as in Example 10was performed, whereby an electrolyte section for evaluation wasproduced.

Comparative Example 3

A precursor solution of a polymer electrolyte composition of ComparativeExample 3 was prepared in the same manner as in Comparative Example 1except that AIBN (polymerization initiator) of Comparative Example 1 waschanged to Irgacure 651 (polymerization initiator) (0.0031 g, 1.21×10⁻⁵mol) as shown in FIG. 12. Incidentally, in Comparative Example 3,(meth)acrylonitrile is not used, and therefore, in the above formula(1), when m and n are set as follows: m+n=10, m and n satisfy thefollowing formulae: m=0 and n=10, and m does not satisfy the followingformula: 1≤m≤5. Thereafter, the same procedure as in Example 6 wasperformed, whereby an electrolyte section for evaluation was produced.

Comparative Example 4

With respect to a precursor solution of a polymer electrolytecomposition of Comparative Example 4, the same procedure as inComparative Example 2 was performed except that AIBN (polymerizationinitiator) of Comparative Example 2 was changed to Irgacure 651(polymerization initiator) (0.0069 g, 2.69×10⁻⁵ mol) andmethacrylonitrile of Comparative Example 2 was changed to acrylonitrile(0.1894 g, 3.57×10⁻³ mol), however, Li-TFSI was not dissolved in PPGAc,and a precursor solution could not be prepared. In the composition ofthe precursor solution of Comparative Example 4, in the above formula(1), when m and n are set as follows: m+n=10, m and n satisfy thefollowing formulae: m=5.5 and n=4.5, and do not satisfy the followingformulae: 1≤m≤5 and 5≤n≤9.

Comparative Example 5

A precursor solution of a polymer electrolyte composition of ComparativeExample 5 was prepared in the same manner as in Comparative Example 3except that PPGAc of Comparative Example 3 was changed to PEGMAc (1.0512g, 2.92×10⁻³ mol) as shown in FIG. 13. Incidentally, in ComparativeExample 5, (meth)acrylonitrile is not used, and therefore, in the aboveformula (1), when m and n are set as follows: m+n=10, m and n satisfythe following formulae: m=0 and n=10, and m does not satisfy thefollowing formula: 1≤m≤5. Thereafter, the same procedure as in Example10 was performed, whereby an electrolyte section for evaluation wasproduced.

Comparative Example 6

With respect to a precursor solution of a polymer electrolytecomposition of Comparative Example 6, the same procedure as inComparative Example 4 was performed except that PPGAc of ComparativeExample 4 was changed to PEGMAc (1.0512 g, 2.92×10⁻³ mol) andacrylonitrile of Comparative Example 4 was changed to methacrylonitrile(0.2395 g, 3.57×10⁻³ mol), however, Li-TFSI was not dissolved in PEGMAc,and a precursor solution could not be prepared. In the composition ofthe precursor solution of Comparative Example 6, in the above formula(1), when m and n are set as follows: m+n=10, m and n satisfy thefollowing formulae: m=5.5 and n=4.5, and do not satisfy the followingformulae: 1≤m≤5 and 5≤n≤9.

Evaluation Methods and Evaluation Results

With respect to the electrolyte sections for evaluation of Examples andComparative Examples, evaluation was performed by the following method,and the results are shown in FIGS. 14 and 15. FIG. 14 is a graph showingexamples of Cole-Cole plots of the impedance spectra of Examples andComparative Examples. FIG. 15 is a table showing the evaluation resultsof the lithium ion conduction property according to Examples andComparative Examples.

Lithium Ion Conduction Property

Each electrolyte section for evaluation was cut out in the shape of adisk having a diameter of 10 mm. A lithium foil having a diameter of 7mm and a thickness of 50 μm was pressed against both front and backsurfaces of the disk to form an electrode, and further, a copper foilhaving a diameter of 7 mm and a thickness of 30 μm was pressed againstboth surfaces of the electrode to form a sample for measurement.Subsequently, by using an impedance analyzer SI 1260 (Solartron, Inc.),the AC impedance of the sample for measurement was measured at an ACvoltage amplitude of 10 mV and a measurement frequency ranging from 10⁷Hz to 10⁻² Hz. Among the Cole-Cole plots of the obtained impedancespectra, those of Example 12 and Comparative Example 5 are shown in FIG.14. In FIG. 14, the horizontal axis represents the real component of thewavenumber (Z′) of the impedance, and the vertical axis represents theimaginary component of the wavenumber (Z″) of the impedance. From theseCole-Cole plots, the total ion conductivity was calculated as the indexof the lithium ion conduction property. The total ion conductivity ofeach of the electrolyte sections for evaluation of Examples andComparative Examples is shown in FIG. 15. Further, the total ionconductivity was evaluated according to the following criteria which arethe same as in Example 1. The results are shown in FIG. 15.

A: The total ion conductivity is 7.0×10⁻⁶ or more.

B: The total ion conductivity is 2.0×10⁻⁶ or more and less than7.0×10⁻⁶.

C: The total ion conductivity is 7.0×10⁻⁷ or more and less than2.0×10⁻⁶.

D: The total ion conductivity is less than 7.0×10⁻⁷.

As shown in FIG. 14, it is found that the internal resistance isdecreased in Example 12 as compared with that in Comparative Example 5.Further, as shown in FIG. 15, Examples 6 to 13 were evaluated as A whichcorresponds to “very suitable”. According to this, it was shown thatExamples 6 to 13 have an excellent lithium ion conduction property.

On the other hand, Comparative Examples 3 and 5 were evaluated as Cwhich corresponds to “not suitable”, and therefore, it was found thatComparative Examples 3 and 5 have a lower lithium ion conductionproperty than Examples. Further, it was found that in ComparativeExamples 4 and 6, a lithium battery could not be produced.

Fourth Embodiment

Electronic Apparatus

An electronic apparatus according to this embodiment will be describedwith reference to FIG. 16. In this embodiment, a wearable apparatus willbe described as an example of the electronic apparatus. FIG. 16 is aschematic view showing a configuration of a wearable apparatus as theelectronic apparatus according to the fourth embodiment.

As shown in FIG. 16, a wearable apparatus 400 of this embodiment is wornon, for example, the wrist WR of the human body using a band 310 like awatch, and is an information apparatus for obtaining information relatedto the human body. The wearable apparatus 400 includes a battery 305, adisplay section 325, a sensor 321, and a processing section 330. As thebattery 305, the lithium battery according to the above-mentionedembodiment is included.

The band 310 is formed in a belt shape using a resin having flexibilitysuch as rubber so as to come into close contact with the wrist WR whenit is worn. In an end portion of the band 310, a binding section (notshown) capable of adjusting the binding position according to thethickness of the wrist WR is provided.

The sensor 321 is disposed on the inner surface side (the wrist WR side)of the band 310 so as to come into contact with the wrist WR when it isworn. The sensor 321 obtains information related to the pulse rate, theblood glucose level, or the like of the human body when it comes intocontact with the wrist WR, and outputs the information to the processingsection 330. As the sensor 321, for example, an optical sensor is used.

The processing section 330 is incorporated in the band 310, and iselectrically connected to the sensor 321 and the display section 325. Asthe processing section 330, for example, an integrated circuit (IC) isused. The processing section 330 performs arithmetic processing of thepulse rate, the blood glucose level, or the like based on the outputfrom the sensor 321, and outputs display data to the display section325.

The display section 325 displays the display data such as the pulse rateor the blood glucose level output from the processing section 330. Asthe display section 325, for example, a light-receiving type liquidcrystal display device is used. The display section 325 is disposed onthe outer surface side (a side opposite to the inner surface on whichthe sensor 321 is disposed) of the band 310 so that a wearer can readthe display data when the wearer wears the wearable apparatus 400.

The battery 305 functions as a power supply source which supplies powerto the display section 325, the sensor 321, and the processing section330. The battery 305 is incorporated in the band 310 in an attachableand detachable manner.

According to the above configuration, the wearable apparatus 400 canobtain information related to the pulse rate or the blood glucose levelof a wearer from the wrist WR and can display it as information such asthe pulse rate or the blood glucose level through arithmetic processingor the like. Further, to the wearable apparatus 400, the lithium batteryaccording to the above-mentioned embodiment having an improved ionconduction property and a large battery capacity in spite of having asmall size is applied, and therefore, the weight can be reduced, andalso the operating time can be increased. Moreover, since the lithiumbattery according to the above-mentioned embodiment is anall-solid-state secondary battery, the battery can be repetitively usedby charging, and also there is no concern about leakage of theelectrolytic solution or the like, and therefore, the wearable apparatus400 which can be used safely for a long period of time can be provided.

In this embodiment, a watch-type wearable apparatus is illustrated asthe wearable apparatus 400, however, the invention is not limitedthereto. The wearable apparatus may be a wearable apparatus to be wornon, for example, the ankle, head, ear, waist, or the like.

The electronic apparatus to which the battery 305 (the lithium batteryaccording to the above-mentioned embodiment) is applied as the powersupply source is not limited to the wearable apparatus 400. As otherelectronic apparatuses, for example, a display to be worn on the headsuch as a head-mounted display, a head-up display, a portable telephone,a portable information terminal, a notebook personal computer, a digitalcamera, a video camera, a music player, a wireless headphone, a portablegaming machine, and the like can be exemplified. These electronicapparatuses may have another function, for example, a data communicationfunction, a gaming function, a recording and playback function, adictionary function, or the like.

Further, the electronic apparatus of this embodiment is not limited tothe use for general consumers, and can also be applied to industrialuse. Moreover, the apparatus to which the lithium battery according tothe above-mentioned embodiment is applied is not limited to electronicapparatuses. For example, the lithium battery according to theabove-mentioned embodiment may be applied as a power supply source for amoving object. Specific examples of the moving object includeautomobiles, motorcycles, forklifts, and flying objects such as unmannedplanes. According to this, a moving object including a battery having animproved ion conduction property as a power supply source can beprovided.

The invention is not limited to the above-mentioned embodiments andvarious changes, modifications, etc. can be added to the above-mentionedembodiments.

The entire disclosure of Japanese Patent Application No. 2016-252561,filed Dec. 27, 2016 is expressly incorporated by reference herein.

What is claimed is:
 1. A polymer electrolyte represented by thefollowing formula (1):

(wherein R¹ and R² are each independently hydrogen or CH₃, R³ is any ofC₂H₄, CH(CH₃)CH₂, and (CH₂)₃, m and n are each a copolymerization ratioof a structural unit in parentheses, and when m and n are set asfollows: m+n=10, m and n satisfy the following formulae: 1≤m≤5 and5≤n≤9, and p is 2 or more and 8 or less).
 2. The polymer electrolyteaccording to claim 1, wherein in the formula (1), when m and n are setas follows: m+n=10, m and n satisfy the following formulae: 2.5≤m≤5 and5≤n≤8.5.
 3. A polymer electrolyte composition comprising the polymerelectrolyte according to claim 1 and a lithium salt compound.
 4. Abattery comprising: an electrolyte section containing the polymerelectrolyte composition according to claim 3; an assembly provided incontact with the electrolyte section and containing an active materialand an electrolyte; and a current collector provided for the electrolytesection through the assembly.
 5. The battery according to claim 4,wherein the electrolyte contains the polymer electrolyte compositionaccording to claim
 3. 6. An electronic apparatus comprising the batteryaccording to claim 4.